Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Well, I think it's fair to say that they're effectively untested prior to rc2. But it's a reasonable posture to take that the features get baked first and the field upgrade procedure gets tested late in the release cycle. Not what I would have expected personally, though, as a former developer of field upgradable consumer electronics. What we used to call the "first article" (the firmware delivered to the manufacturing line) was routinely unusable for much of anything beyond the first-time setup procedure and download of over-the-air updates, and a firmware upgrade/downgrade cycle was the first step in smoke testing every subsequent release candidate. Seems like the concerns (the high cost of upgrade failure and likelihood of permanently losing customer trust) are similar. But when one doesn't face a hard August ship date for the first article for a Christmas-shopping-season product release, I suppose one can afford a different order of operations. I am very grateful for the ZooKeeper software and for the care and resources that its maintainers and community put into its integrity and vitality. I value the release engineering process, and don't take for granted that any given snapshot off of a release branch is fit for purpose. At the same time, I'd feel more confident recommending it for more use cases within the engineering organizations I support if there were stronger test scaffolding around version migration and similar production operations. That's something I'd like to help with in the future, resources permitting. Cheers, - Michael On Wed, Feb 12, 2020 at 4:16 AM Andor Molnar wrote: > Hi Michael, > > "if we can get to rc2 without noticing a showstopper…” > > 200% disagree with this. > > The whole point of release voting system is to identify problems no matter > how big they are. The message of finding a showstopper for me is that > people paying attention and accurately testing the release. This is a very > good thing and emphasises how much effort the ZooKeeper community is > putting into every single release. Otherwise we could just set up a Jenkins > job which creates and publishes a new release in every six months and say > good luck with them. > > I admit that currently we don’t have (rolling) upgrade tests, but I feel > demand from the community to fill this gap. > > “rolling upgrades (and mixed ensembles generally) are effectively untested” > > Not true. That’s exactly what we are currently doing (manually for now). > > "there have to be a hundred corner cases beyond the MultiAddress issue” > > Sure thing. True for every new feature in every release. That’s why I’m > happy disabling it by default. People usually don’t pick up releases ending > with .0, production upgrades are expected from .1 or .2 or maybe later > depending on how much risk would like to be taken. > > Andor > > > > > On 2020. Feb 11., at 23:35, Michael K. Edwards > wrote: > > > > I think it would be prudent to emphasize in the release notes that > rolling > > upgrades (and mixed ensembles generally) are effectively untested. That > > this was, in practice, a non-goal of this release cycle. Because if we > can > > get to rc2 without noticing a showstopper, clearly it's not something > that > > anyone has gotten around to attempting; and there have to be a hundred > > corner cases beyond the MultiAddress issue. > > > > On Tue, Feb 11, 2020 at 12:27 PM Szalay-Bekő Máté < > > szalay.beko.m...@gmail.com> wrote: > > > >> I see the main problem here in the fact that we are missing proper > >> versioning in the leader election / quorum protocols. I tried to simply > >> implement backward compatibility in 3.6, but it didn't solve the > problem. > >> The new code understands the old protocol, but it can not decide when to > >> use the new or the old protocol during connection initiation. So the old > >> servers can not read the new init messages and we still temporarly end > up > >> having two partitions during rolling restart. > >> > >> I already suggested two ways to handle this later, but I think for 3.6.0 > >> now the simplest solution is to disable the new MultiAddress feature and > >> stick to the old protocol version by default. Plus extend the > >> documentation with the note, that enabling the MultiAddress feature is > not > >> possible during a rolling upgrade, but it needs to be done with a > separate > >> rolling restart. With this approach, the rolling restart should "just > work" > >> with the 3.4 / 3.5 configs and we don't require any extra step / > >> configuration from the users, unless they want to use the new feature. I > >> plan to submit a PR with these changes tomorrow to ZOOKEEPER-3720, if > there > >> isn't any different opinion. > >> > >> P.S. For 4.0 we might need to put some extra thinking into backward > >> compatibility / versioning for the quorum and client protocols. > >> > >> > >> On Tue, Feb 11, 2020, 20:44 Michael K. Edwards > >> wrote: > >> > >>> I hate to say it, but I think
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
FYI: PR just submitted, see https://github.com/apache/zookeeper/pull/1251 any comments welcomed! :) Kind regards, Mate On Wed, Feb 12, 2020 at 1:16 PM Andor Molnar wrote: > Hi Michael, > > "if we can get to rc2 without noticing a showstopper…” > > 200% disagree with this. > > The whole point of release voting system is to identify problems no matter > how big they are. The message of finding a showstopper for me is that > people paying attention and accurately testing the release. This is a very > good thing and emphasises how much effort the ZooKeeper community is > putting into every single release. Otherwise we could just set up a Jenkins > job which creates and publishes a new release in every six months and say > good luck with them. > > I admit that currently we don’t have (rolling) upgrade tests, but I feel > demand from the community to fill this gap. > > “rolling upgrades (and mixed ensembles generally) are effectively untested” > > Not true. That’s exactly what we are currently doing (manually for now). > > "there have to be a hundred corner cases beyond the MultiAddress issue” > > Sure thing. True for every new feature in every release. That’s why I’m > happy disabling it by default. People usually don’t pick up releases ending > with .0, production upgrades are expected from .1 or .2 or maybe later > depending on how much risk would like to be taken. > > Andor > > > > > On 2020. Feb 11., at 23:35, Michael K. Edwards > wrote: > > > > I think it would be prudent to emphasize in the release notes that > rolling > > upgrades (and mixed ensembles generally) are effectively untested. That > > this was, in practice, a non-goal of this release cycle. Because if we > can > > get to rc2 without noticing a showstopper, clearly it's not something > that > > anyone has gotten around to attempting; and there have to be a hundred > > corner cases beyond the MultiAddress issue. > > > > On Tue, Feb 11, 2020 at 12:27 PM Szalay-Bekő Máté < > > szalay.beko.m...@gmail.com> wrote: > > > >> I see the main problem here in the fact that we are missing proper > >> versioning in the leader election / quorum protocols. I tried to simply > >> implement backward compatibility in 3.6, but it didn't solve the > problem. > >> The new code understands the old protocol, but it can not decide when to > >> use the new or the old protocol during connection initiation. So the old > >> servers can not read the new init messages and we still temporarly end > up > >> having two partitions during rolling restart. > >> > >> I already suggested two ways to handle this later, but I think for 3.6.0 > >> now the simplest solution is to disable the new MultiAddress feature and > >> stick to the old protocol version by default. Plus extend the > >> documentation with the note, that enabling the MultiAddress feature is > not > >> possible during a rolling upgrade, but it needs to be done with a > separate > >> rolling restart. With this approach, the rolling restart should "just > work" > >> with the 3.4 / 3.5 configs and we don't require any extra step / > >> configuration from the users, unless they want to use the new feature. I > >> plan to submit a PR with these changes tomorrow to ZOOKEEPER-3720, if > there > >> isn't any different opinion. > >> > >> P.S. For 4.0 we might need to put some extra thinking into backward > >> compatibility / versioning for the quorum and client protocols. > >> > >> > >> On Tue, Feb 11, 2020, 20:44 Michael K. Edwards > >> wrote: > >> > >>> I hate to say it, but I think 3.6.0 should release as is. It is > >>> impossible > >>> to *reliably* retrofit backwards compatibility / interoperability onto > a > >>> release that was engineered from the beginning without that goal. > Learn > >>> the lesson, set goals differently in the future. > >>> > >>> On Tue, Feb 11, 2020 at 9:41 AM Szalay-Bekő Máté < > >>> szalay.beko.m...@gmail.com> > >>> wrote: > >>> > FYI: I created these scripts for my local tests: > https://github.com/symat/zk-rolling-upgrade-test > > For the long term I would also add some script that actually monitors > >>> the > state of the quorum and also runs continuous traffic, not just 1-2 > smoketests after each restart. But I don't know how important this > would > be. > > On Tue, Feb 11, 2020 at 5:25 PM Enrico Olivelli > wrote: > > > Il giorno mar 11 feb 2020 alle ore 17:17 Andor Molnar > > ha scritto: > >> > >> The most obvious one which crosses my mind is that I previously > >>> worked > > on: > >> > >> 1) run old version cluster, > >> 2) connect to each node and run smoke tests, > >> 3) restart one node with new code, > >> 4) goto 2) until all nodes are upgraded > >> > >> I think this wouldn’t work in a “unit test”, we probably need a > separate > > Jenkins job and a nice python script to do this. > >> > >> Andor > >> > >> > >> > >> > >>> On 2020.
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Hi Michael, "if we can get to rc2 without noticing a showstopper…” 200% disagree with this. The whole point of release voting system is to identify problems no matter how big they are. The message of finding a showstopper for me is that people paying attention and accurately testing the release. This is a very good thing and emphasises how much effort the ZooKeeper community is putting into every single release. Otherwise we could just set up a Jenkins job which creates and publishes a new release in every six months and say good luck with them. I admit that currently we don’t have (rolling) upgrade tests, but I feel demand from the community to fill this gap. “rolling upgrades (and mixed ensembles generally) are effectively untested” Not true. That’s exactly what we are currently doing (manually for now). "there have to be a hundred corner cases beyond the MultiAddress issue” Sure thing. True for every new feature in every release. That’s why I’m happy disabling it by default. People usually don’t pick up releases ending with .0, production upgrades are expected from .1 or .2 or maybe later depending on how much risk would like to be taken. Andor > On 2020. Feb 11., at 23:35, Michael K. Edwards wrote: > > I think it would be prudent to emphasize in the release notes that rolling > upgrades (and mixed ensembles generally) are effectively untested. That > this was, in practice, a non-goal of this release cycle. Because if we can > get to rc2 without noticing a showstopper, clearly it's not something that > anyone has gotten around to attempting; and there have to be a hundred > corner cases beyond the MultiAddress issue. > > On Tue, Feb 11, 2020 at 12:27 PM Szalay-Bekő Máté < > szalay.beko.m...@gmail.com> wrote: > >> I see the main problem here in the fact that we are missing proper >> versioning in the leader election / quorum protocols. I tried to simply >> implement backward compatibility in 3.6, but it didn't solve the problem. >> The new code understands the old protocol, but it can not decide when to >> use the new or the old protocol during connection initiation. So the old >> servers can not read the new init messages and we still temporarly end up >> having two partitions during rolling restart. >> >> I already suggested two ways to handle this later, but I think for 3.6.0 >> now the simplest solution is to disable the new MultiAddress feature and >> stick to the old protocol version by default. Plus extend the >> documentation with the note, that enabling the MultiAddress feature is not >> possible during a rolling upgrade, but it needs to be done with a separate >> rolling restart. With this approach, the rolling restart should "just work" >> with the 3.4 / 3.5 configs and we don't require any extra step / >> configuration from the users, unless they want to use the new feature. I >> plan to submit a PR with these changes tomorrow to ZOOKEEPER-3720, if there >> isn't any different opinion. >> >> P.S. For 4.0 we might need to put some extra thinking into backward >> compatibility / versioning for the quorum and client protocols. >> >> >> On Tue, Feb 11, 2020, 20:44 Michael K. Edwards >> wrote: >> >>> I hate to say it, but I think 3.6.0 should release as is. It is >>> impossible >>> to *reliably* retrofit backwards compatibility / interoperability onto a >>> release that was engineered from the beginning without that goal. Learn >>> the lesson, set goals differently in the future. >>> >>> On Tue, Feb 11, 2020 at 9:41 AM Szalay-Bekő Máté < >>> szalay.beko.m...@gmail.com> >>> wrote: >>> FYI: I created these scripts for my local tests: https://github.com/symat/zk-rolling-upgrade-test For the long term I would also add some script that actually monitors >>> the state of the quorum and also runs continuous traffic, not just 1-2 smoketests after each restart. But I don't know how important this would be. On Tue, Feb 11, 2020 at 5:25 PM Enrico Olivelli wrote: > Il giorno mar 11 feb 2020 alle ore 17:17 Andor Molnar > ha scritto: >> >> The most obvious one which crosses my mind is that I previously >>> worked > on: >> >> 1) run old version cluster, >> 2) connect to each node and run smoke tests, >> 3) restart one node with new code, >> 4) goto 2) until all nodes are upgraded >> >> I think this wouldn’t work in a “unit test”, we probably need a separate > Jenkins job and a nice python script to do this. >> >> Andor >> >> >> >> >>> On 2020. Feb 11., at 16:38, Patrick Hunt >>> wrote: >>> >>> Anyone have ideas how we could add testing for upgrade? Obviously > something >>> we're missing, esp given it's import. > > I will send an email next days with a proposal. > btw my idea is very like Andor's one > > Once we have an automatic environment we can launch from Jenkins > >
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Michael, your points are valid. I would like to see the proposal from Mate. Up to ZOOKEEPER-3188 no other patch in 3.6 (from my limited point of view) introduced changes in quorum peer protocol to make it non compatible with 3.5. Enrico Il giorno mar 11 feb 2020 alle ore 23:35 Michael K. Edwards ha scritto: > > I think it would be prudent to emphasize in the release notes that rolling > upgrades (and mixed ensembles generally) are effectively untested. That > this was, in practice, a non-goal of this release cycle. Because if we can > get to rc2 without noticing a showstopper, clearly it's not something that > anyone has gotten around to attempting; and there have to be a hundred > corner cases beyond the MultiAddress issue. > > On Tue, Feb 11, 2020 at 12:27 PM Szalay-Bekő Máté < > szalay.beko.m...@gmail.com> wrote: > > > I see the main problem here in the fact that we are missing proper > > versioning in the leader election / quorum protocols. I tried to simply > > implement backward compatibility in 3.6, but it didn't solve the problem. > > The new code understands the old protocol, but it can not decide when to > > use the new or the old protocol during connection initiation. So the old > > servers can not read the new init messages and we still temporarly end up > > having two partitions during rolling restart. > > > > I already suggested two ways to handle this later, but I think for 3.6.0 > > now the simplest solution is to disable the new MultiAddress feature and > > stick to the old protocol version by default. Plus extend the > > documentation with the note, that enabling the MultiAddress feature is not > > possible during a rolling upgrade, but it needs to be done with a separate > > rolling restart. With this approach, the rolling restart should "just work" > > with the 3.4 / 3.5 configs and we don't require any extra step / > > configuration from the users, unless they want to use the new feature. I > > plan to submit a PR with these changes tomorrow to ZOOKEEPER-3720, if there > > isn't any different opinion. > > > > P.S. For 4.0 we might need to put some extra thinking into backward > > compatibility / versioning for the quorum and client protocols. > > > > > > On Tue, Feb 11, 2020, 20:44 Michael K. Edwards > > wrote: > > > >> I hate to say it, but I think 3.6.0 should release as is. It is > >> impossible > >> to *reliably* retrofit backwards compatibility / interoperability onto a > >> release that was engineered from the beginning without that goal. Learn > >> the lesson, set goals differently in the future. > >> > >> On Tue, Feb 11, 2020 at 9:41 AM Szalay-Bekő Máté < > >> szalay.beko.m...@gmail.com> > >> wrote: > >> > >> > FYI: I created these scripts for my local tests: > >> > https://github.com/symat/zk-rolling-upgrade-test > >> > > >> > For the long term I would also add some script that actually monitors > >> the > >> > state of the quorum and also runs continuous traffic, not just 1-2 > >> > smoketests after each restart. But I don't know how important this would > >> > be. > >> > > >> > On Tue, Feb 11, 2020 at 5:25 PM Enrico Olivelli > >> > wrote: > >> > > >> > > Il giorno mar 11 feb 2020 alle ore 17:17 Andor Molnar > >> > > ha scritto: > >> > > > > >> > > > The most obvious one which crosses my mind is that I previously > >> worked > >> > > on: > >> > > > > >> > > > 1) run old version cluster, > >> > > > 2) connect to each node and run smoke tests, > >> > > > 3) restart one node with new code, > >> > > > 4) goto 2) until all nodes are upgraded > >> > > > > >> > > > I think this wouldn’t work in a “unit test”, we probably need a > >> > separate > >> > > Jenkins job and a nice python script to do this. > >> > > > > >> > > > Andor > >> > > > > >> > > > > >> > > > > >> > > > > >> > > > > On 2020. Feb 11., at 16:38, Patrick Hunt > >> wrote: > >> > > > > > >> > > > > Anyone have ideas how we could add testing for upgrade? Obviously > >> > > something > >> > > > > we're missing, esp given it's import. > >> > > > >> > > I will send an email next days with a proposal. > >> > > btw my idea is very like Andor's one > >> > > > >> > > Once we have an automatic environment we can launch from Jenkins > >> > > > >> > > Enrico > >> > > > >> > > > >> > > > > > >> > > > > Patrick > >> > > > > > >> > > > > On Tue, Feb 11, 2020 at 12:40 AM Enrico Olivelli < > >> > eolive...@gmail.com> > >> > > > > wrote: > >> > > > > > >> > > > >> Il giorno mar 11 feb 2020 alle ore 09:12 Szalay-Bekő Máté > >> > > > >> ha scritto: > >> > > > >>> > >> > > > >>> Hi All, > >> > > > >>> > >> > > > >>> about the question from Michael: > >> > > > Regarding the fix, can we just make 3.6.0 aware of the old > >> > protocol > >> > > and > >> > > > speak old message format when it's talking to old server? > >> > > > >>> > >> > > > >>> In this particular case, it might be enough. The protocol change > >> > > happened > >> > > > >>> now in the 'initial message' sent by the QuorumCnxManager. > >> Maybe it > >>
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
I think it would be prudent to emphasize in the release notes that rolling upgrades (and mixed ensembles generally) are effectively untested. That this was, in practice, a non-goal of this release cycle. Because if we can get to rc2 without noticing a showstopper, clearly it's not something that anyone has gotten around to attempting; and there have to be a hundred corner cases beyond the MultiAddress issue. On Tue, Feb 11, 2020 at 12:27 PM Szalay-Bekő Máté < szalay.beko.m...@gmail.com> wrote: > I see the main problem here in the fact that we are missing proper > versioning in the leader election / quorum protocols. I tried to simply > implement backward compatibility in 3.6, but it didn't solve the problem. > The new code understands the old protocol, but it can not decide when to > use the new or the old protocol during connection initiation. So the old > servers can not read the new init messages and we still temporarly end up > having two partitions during rolling restart. > > I already suggested two ways to handle this later, but I think for 3.6.0 > now the simplest solution is to disable the new MultiAddress feature and > stick to the old protocol version by default. Plus extend the > documentation with the note, that enabling the MultiAddress feature is not > possible during a rolling upgrade, but it needs to be done with a separate > rolling restart. With this approach, the rolling restart should "just work" > with the 3.4 / 3.5 configs and we don't require any extra step / > configuration from the users, unless they want to use the new feature. I > plan to submit a PR with these changes tomorrow to ZOOKEEPER-3720, if there > isn't any different opinion. > > P.S. For 4.0 we might need to put some extra thinking into backward > compatibility / versioning for the quorum and client protocols. > > > On Tue, Feb 11, 2020, 20:44 Michael K. Edwards > wrote: > >> I hate to say it, but I think 3.6.0 should release as is. It is >> impossible >> to *reliably* retrofit backwards compatibility / interoperability onto a >> release that was engineered from the beginning without that goal. Learn >> the lesson, set goals differently in the future. >> >> On Tue, Feb 11, 2020 at 9:41 AM Szalay-Bekő Máté < >> szalay.beko.m...@gmail.com> >> wrote: >> >> > FYI: I created these scripts for my local tests: >> > https://github.com/symat/zk-rolling-upgrade-test >> > >> > For the long term I would also add some script that actually monitors >> the >> > state of the quorum and also runs continuous traffic, not just 1-2 >> > smoketests after each restart. But I don't know how important this would >> > be. >> > >> > On Tue, Feb 11, 2020 at 5:25 PM Enrico Olivelli >> > wrote: >> > >> > > Il giorno mar 11 feb 2020 alle ore 17:17 Andor Molnar >> > > ha scritto: >> > > > >> > > > The most obvious one which crosses my mind is that I previously >> worked >> > > on: >> > > > >> > > > 1) run old version cluster, >> > > > 2) connect to each node and run smoke tests, >> > > > 3) restart one node with new code, >> > > > 4) goto 2) until all nodes are upgraded >> > > > >> > > > I think this wouldn’t work in a “unit test”, we probably need a >> > separate >> > > Jenkins job and a nice python script to do this. >> > > > >> > > > Andor >> > > > >> > > > >> > > > >> > > > >> > > > > On 2020. Feb 11., at 16:38, Patrick Hunt >> wrote: >> > > > > >> > > > > Anyone have ideas how we could add testing for upgrade? Obviously >> > > something >> > > > > we're missing, esp given it's import. >> > > >> > > I will send an email next days with a proposal. >> > > btw my idea is very like Andor's one >> > > >> > > Once we have an automatic environment we can launch from Jenkins >> > > >> > > Enrico >> > > >> > > >> > > > > >> > > > > Patrick >> > > > > >> > > > > On Tue, Feb 11, 2020 at 12:40 AM Enrico Olivelli < >> > eolive...@gmail.com> >> > > > > wrote: >> > > > > >> > > > >> Il giorno mar 11 feb 2020 alle ore 09:12 Szalay-Bekő Máté >> > > > >> ha scritto: >> > > > >>> >> > > > >>> Hi All, >> > > > >>> >> > > > >>> about the question from Michael: >> > > > Regarding the fix, can we just make 3.6.0 aware of the old >> > protocol >> > > and >> > > > speak old message format when it's talking to old server? >> > > > >>> >> > > > >>> In this particular case, it might be enough. The protocol change >> > > happened >> > > > >>> now in the 'initial message' sent by the QuorumCnxManager. >> Maybe it >> > > is >> > > > >> not >> > > > >>> a problem if the new servers can not initiate channels to the >> old >> > > > >> servers, >> > > > >>> maybe it is enough if these channel gets initiated by the old >> > servers >> > > > >> only. >> > > > >>> I will test it quickly. >> > > > >>> >> > > > >>> Although I have no idea if any other thing changed in the quorum >> > > protocol >> > > > >>> between 3.5 and 3.6. In other cases it might not be enough if >> the >> > new >> > > > >>> servers can understand the old messages, as the old servers can >>
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Hi Andor, this is almost exactly what I proposed. More precisely: 1) First we make multi-address feature disabled by default. 2) If disabled, quorum protocol automatically uses the old protocol version which lets 3.5 and 3.6 communicate smoothly. The code in 3.6.0 will be able to understand both the old and the new protocols, but it will send the messages in the old protocol by default. 3) Once the user finished the first rolling upgrade, the cluster is running 3.6 and communicating with old protocol. 4) If user wants to enable multi-address feature (I think that’s quite rare anyway), another rolling restart is needed, but this time there will be no partitions, as all the members of the cluster will understand both protocols. At least this is the theory :) I still have to verify this with tests. Kind regards, Mate On Tue, Feb 11, 2020, 22:10 Andor Molnar wrote: > Mate, > > Let me reiterate to see if I understand you correctly: > > 1) First we make multi-address feature disabled by default. > > 2) If disabled, quorum protocol automatically uses the old protocol > version which lets 3.5 and 3.6 communicate smoothly. > > 3) Once the user finished the first rolling restart, the cluster is > running 3.6 and communicating with old protocol. > > 4) If user wants to enable multi-address feature (I think that’s quite > rare anyway), another rolling restart is needed, but this time partitions > cannot be avoided. > > Is that accurate? > > I think it’s not the end of the world. > > Andor > > > > > > On 2020. Feb 11., at 21:27, Szalay-Bekő Máté > wrote: > > > > I see the main problem here in the fact that we are missing proper > > versioning in the leader election / quorum protocols. I tried to simply > > implement backward compatibility in 3.6, but it didn't solve the problem. > > The new code understands the old protocol, but it can not decide when to > > use the new or the old protocol during connection initiation. So the old > > servers can not read the new init messages and we still temporarly end up > > having two partitions during rolling restart. > > > > I already suggested two ways to handle this later, but I think for 3.6.0 > > now the simplest solution is to disable the new MultiAddress feature and > > stick to the old protocol version by default. Plus extend the > documentation > > with the note, that enabling the MultiAddress feature is not possible > > during a rolling upgrade, but it needs to be done with a separate rolling > > restart. With this approach, the rolling restart should "just work" with > > the 3.4 / 3.5 configs and we don't require any extra step / configuration > > from the users, unless they want to use the new feature. I plan to > submit a > > PR with these changes tomorrow to ZOOKEEPER-3720, if there isn't any > > different opinion. > > > > P.S. For 4.0 we might need to put some extra thinking into backward > > compatibility / versioning for the quorum and client protocols. > > > > > > On Tue, Feb 11, 2020, 20:44 Michael K. Edwards > > wrote: > > > >> I hate to say it, but I think 3.6.0 should release as is. It is > impossible > >> to *reliably* retrofit backwards compatibility / interoperability onto a > >> release that was engineered from the beginning without that goal. Learn > >> the lesson, set goals differently in the future. > >> > >> On Tue, Feb 11, 2020 at 9:41 AM Szalay-Bekő Máté < > >> szalay.beko.m...@gmail.com> > >> wrote: > >> > >>> FYI: I created these scripts for my local tests: > >>> https://github.com/symat/zk-rolling-upgrade-test > >>> > >>> For the long term I would also add some script that actually monitors > the > >>> state of the quorum and also runs continuous traffic, not just 1-2 > >>> smoketests after each restart. But I don't know how important this > would > >>> be. > >>> > >>> On Tue, Feb 11, 2020 at 5:25 PM Enrico Olivelli > >>> wrote: > >>> > Il giorno mar 11 feb 2020 alle ore 17:17 Andor Molnar > ha scritto: > > > > The most obvious one which crosses my mind is that I previously > >> worked > on: > > > > 1) run old version cluster, > > 2) connect to each node and run smoke tests, > > 3) restart one node with new code, > > 4) goto 2) until all nodes are upgraded > > > > I think this wouldn’t work in a “unit test”, we probably need a > >>> separate > Jenkins job and a nice python script to do this. > > > > Andor > > > > > > > > > >> On 2020. Feb 11., at 16:38, Patrick Hunt wrote: > >> > >> Anyone have ideas how we could add testing for upgrade? Obviously > something > >> we're missing, esp given it's import. > > I will send an email next days with a proposal. > btw my idea is very like Andor's one > > Once we have an automatic environment we can launch from Jenkins > > Enrico > > > >> > >> Patrick > >> > >> On Tue, Feb 11, 2020 at 12:40 AM Enrico Olivelli < > >>>
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Mate, Let me reiterate to see if I understand you correctly: 1) First we make multi-address feature disabled by default. 2) If disabled, quorum protocol automatically uses the old protocol version which lets 3.5 and 3.6 communicate smoothly. 3) Once the user finished the first rolling restart, the cluster is running 3.6 and communicating with old protocol. 4) If user wants to enable multi-address feature (I think that’s quite rare anyway), another rolling restart is needed, but this time partitions cannot be avoided. Is that accurate? I think it’s not the end of the world. Andor > On 2020. Feb 11., at 21:27, Szalay-Bekő Máté > wrote: > > I see the main problem here in the fact that we are missing proper > versioning in the leader election / quorum protocols. I tried to simply > implement backward compatibility in 3.6, but it didn't solve the problem. > The new code understands the old protocol, but it can not decide when to > use the new or the old protocol during connection initiation. So the old > servers can not read the new init messages and we still temporarly end up > having two partitions during rolling restart. > > I already suggested two ways to handle this later, but I think for 3.6.0 > now the simplest solution is to disable the new MultiAddress feature and > stick to the old protocol version by default. Plus extend the documentation > with the note, that enabling the MultiAddress feature is not possible > during a rolling upgrade, but it needs to be done with a separate rolling > restart. With this approach, the rolling restart should "just work" with > the 3.4 / 3.5 configs and we don't require any extra step / configuration > from the users, unless they want to use the new feature. I plan to submit a > PR with these changes tomorrow to ZOOKEEPER-3720, if there isn't any > different opinion. > > P.S. For 4.0 we might need to put some extra thinking into backward > compatibility / versioning for the quorum and client protocols. > > > On Tue, Feb 11, 2020, 20:44 Michael K. Edwards > wrote: > >> I hate to say it, but I think 3.6.0 should release as is. It is impossible >> to *reliably* retrofit backwards compatibility / interoperability onto a >> release that was engineered from the beginning without that goal. Learn >> the lesson, set goals differently in the future. >> >> On Tue, Feb 11, 2020 at 9:41 AM Szalay-Bekő Máté < >> szalay.beko.m...@gmail.com> >> wrote: >> >>> FYI: I created these scripts for my local tests: >>> https://github.com/symat/zk-rolling-upgrade-test >>> >>> For the long term I would also add some script that actually monitors the >>> state of the quorum and also runs continuous traffic, not just 1-2 >>> smoketests after each restart. But I don't know how important this would >>> be. >>> >>> On Tue, Feb 11, 2020 at 5:25 PM Enrico Olivelli >>> wrote: >>> Il giorno mar 11 feb 2020 alle ore 17:17 Andor Molnar ha scritto: > > The most obvious one which crosses my mind is that I previously >> worked on: > > 1) run old version cluster, > 2) connect to each node and run smoke tests, > 3) restart one node with new code, > 4) goto 2) until all nodes are upgraded > > I think this wouldn’t work in a “unit test”, we probably need a >>> separate Jenkins job and a nice python script to do this. > > Andor > > > > >> On 2020. Feb 11., at 16:38, Patrick Hunt wrote: >> >> Anyone have ideas how we could add testing for upgrade? Obviously something >> we're missing, esp given it's import. I will send an email next days with a proposal. btw my idea is very like Andor's one Once we have an automatic environment we can launch from Jenkins Enrico >> >> Patrick >> >> On Tue, Feb 11, 2020 at 12:40 AM Enrico Olivelli < >>> eolive...@gmail.com> >> wrote: >> >>> Il giorno mar 11 feb 2020 alle ore 09:12 Szalay-Bekő Máté >>> ha scritto: Hi All, about the question from Michael: > Regarding the fix, can we just make 3.6.0 aware of the old >>> protocol and > speak old message format when it's talking to old server? In this particular case, it might be enough. The protocol change happened now in the 'initial message' sent by the QuorumCnxManager. Maybe >> it is >>> not a problem if the new servers can not initiate channels to the old >>> servers, maybe it is enough if these channel gets initiated by the old >>> servers >>> only. I will test it quickly. Although I have no idea if any other thing changed in the quorum protocol between 3.5 and 3.6. In other cases it might not be enough if the >>> new servers can understand the old messages, as the old servers can break by not understanding the
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
>> but it didn't solve the problem. Yes, the constraint is 3.6.0 has to default to old protocol version so the outgoing message is backward compatible. If we do this, then it's essentially the "the simplest solution" proposed. >> disable the new MultiAddress feature and stick to the old protocol version by default. +1. I would trade the capability of doing seamless rolling upgrade over a new feature that's not absolutely required for operations of ZooKeeper. We can turn the feature on by default in future releases which has better built in b/f compatibility. >> One option can be to make a patch also for 3.5 to have a version which supports both protocol versions. This is another solution - historically we did similar on requiring a certain upgrade path when a new feature changed wire protocol such as dynamic reconfiguration requires 3.4.x first upgrades to 3.4.6 then to 3.5.0. We can start doing this from next 3.5 release so it's forward compatible. >> I don't think the quorum will always be up (e.g. between older 3.4 versions and 3.5). The only case this is not holding is upgrading of versions older than 3.4.6 to 3.5 as previously commented afaik. On Tue, Feb 11, 2020 at 12:27 PM Szalay-Bekő Máté < szalay.beko.m...@gmail.com> wrote: > I see the main problem here in the fact that we are missing proper > versioning in the leader election / quorum protocols. I tried to simply > implement backward compatibility in 3.6, but it didn't solve the problem. > The new code understands the old protocol, but it can not decide when to > use the new or the old protocol during connection initiation. So the old > servers can not read the new init messages and we still temporarly end up > having two partitions during rolling restart. > > I already suggested two ways to handle this later, but I think for 3.6.0 > now the simplest solution is to disable the new MultiAddress feature and > stick to the old protocol version by default. Plus extend the documentation > with the note, that enabling the MultiAddress feature is not possible > during a rolling upgrade, but it needs to be done with a separate rolling > restart. With this approach, the rolling restart should "just work" with > the 3.4 / 3.5 configs and we don't require any extra step / configuration > from the users, unless they want to use the new feature. I plan to submit a > PR with these changes tomorrow to ZOOKEEPER-3720, if there isn't any > different opinion. > > P.S. For 4.0 we might need to put some extra thinking into backward > compatibility / versioning for the quorum and client protocols. > > > On Tue, Feb 11, 2020, 20:44 Michael K. Edwards > wrote: > > > I hate to say it, but I think 3.6.0 should release as is. It is > impossible > > to *reliably* retrofit backwards compatibility / interoperability onto a > > release that was engineered from the beginning without that goal. Learn > > the lesson, set goals differently in the future. > > > > On Tue, Feb 11, 2020 at 9:41 AM Szalay-Bekő Máté < > > szalay.beko.m...@gmail.com> > > wrote: > > > > > FYI: I created these scripts for my local tests: > > > https://github.com/symat/zk-rolling-upgrade-test > > > > > > For the long term I would also add some script that actually monitors > the > > > state of the quorum and also runs continuous traffic, not just 1-2 > > > smoketests after each restart. But I don't know how important this > would > > > be. > > > > > > On Tue, Feb 11, 2020 at 5:25 PM Enrico Olivelli > > > wrote: > > > > > > > Il giorno mar 11 feb 2020 alle ore 17:17 Andor Molnar > > > > ha scritto: > > > > > > > > > > The most obvious one which crosses my mind is that I previously > > worked > > > > on: > > > > > > > > > > 1) run old version cluster, > > > > > 2) connect to each node and run smoke tests, > > > > > 3) restart one node with new code, > > > > > 4) goto 2) until all nodes are upgraded > > > > > > > > > > I think this wouldn’t work in a “unit test”, we probably need a > > > separate > > > > Jenkins job and a nice python script to do this. > > > > > > > > > > Andor > > > > > > > > > > > > > > > > > > > > > > > > > > On 2020. Feb 11., at 16:38, Patrick Hunt > wrote: > > > > > > > > > > > > Anyone have ideas how we could add testing for upgrade? Obviously > > > > something > > > > > > we're missing, esp given it's import. > > > > > > > > I will send an email next days with a proposal. > > > > btw my idea is very like Andor's one > > > > > > > > Once we have an automatic environment we can launch from Jenkins > > > > > > > > Enrico > > > > > > > > > > > > > > > > > > > > Patrick > > > > > > > > > > > > On Tue, Feb 11, 2020 at 12:40 AM Enrico Olivelli < > > > eolive...@gmail.com> > > > > > > wrote: > > > > > > > > > > > >> Il giorno mar 11 feb 2020 alle ore 09:12 Szalay-Bekő Máté > > > > > >> ha scritto: > > > > > >>> > > > > > >>> Hi All, > > > > > >>> > > > > > >>> about the question from Michael: > > > > > Regarding the fix, can we just make 3.6.0 aware of the old > > >
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
I see the main problem here in the fact that we are missing proper versioning in the leader election / quorum protocols. I tried to simply implement backward compatibility in 3.6, but it didn't solve the problem. The new code understands the old protocol, but it can not decide when to use the new or the old protocol during connection initiation. So the old servers can not read the new init messages and we still temporarly end up having two partitions during rolling restart. I already suggested two ways to handle this later, but I think for 3.6.0 now the simplest solution is to disable the new MultiAddress feature and stick to the old protocol version by default. Plus extend the documentation with the note, that enabling the MultiAddress feature is not possible during a rolling upgrade, but it needs to be done with a separate rolling restart. With this approach, the rolling restart should "just work" with the 3.4 / 3.5 configs and we don't require any extra step / configuration from the users, unless they want to use the new feature. I plan to submit a PR with these changes tomorrow to ZOOKEEPER-3720, if there isn't any different opinion. P.S. For 4.0 we might need to put some extra thinking into backward compatibility / versioning for the quorum and client protocols. On Tue, Feb 11, 2020, 20:44 Michael K. Edwards wrote: > I hate to say it, but I think 3.6.0 should release as is. It is impossible > to *reliably* retrofit backwards compatibility / interoperability onto a > release that was engineered from the beginning without that goal. Learn > the lesson, set goals differently in the future. > > On Tue, Feb 11, 2020 at 9:41 AM Szalay-Bekő Máté < > szalay.beko.m...@gmail.com> > wrote: > > > FYI: I created these scripts for my local tests: > > https://github.com/symat/zk-rolling-upgrade-test > > > > For the long term I would also add some script that actually monitors the > > state of the quorum and also runs continuous traffic, not just 1-2 > > smoketests after each restart. But I don't know how important this would > > be. > > > > On Tue, Feb 11, 2020 at 5:25 PM Enrico Olivelli > > wrote: > > > > > Il giorno mar 11 feb 2020 alle ore 17:17 Andor Molnar > > > ha scritto: > > > > > > > > The most obvious one which crosses my mind is that I previously > worked > > > on: > > > > > > > > 1) run old version cluster, > > > > 2) connect to each node and run smoke tests, > > > > 3) restart one node with new code, > > > > 4) goto 2) until all nodes are upgraded > > > > > > > > I think this wouldn’t work in a “unit test”, we probably need a > > separate > > > Jenkins job and a nice python script to do this. > > > > > > > > Andor > > > > > > > > > > > > > > > > > > > > > On 2020. Feb 11., at 16:38, Patrick Hunt wrote: > > > > > > > > > > Anyone have ideas how we could add testing for upgrade? Obviously > > > something > > > > > we're missing, esp given it's import. > > > > > > I will send an email next days with a proposal. > > > btw my idea is very like Andor's one > > > > > > Once we have an automatic environment we can launch from Jenkins > > > > > > Enrico > > > > > > > > > > > > > > > > Patrick > > > > > > > > > > On Tue, Feb 11, 2020 at 12:40 AM Enrico Olivelli < > > eolive...@gmail.com> > > > > > wrote: > > > > > > > > > >> Il giorno mar 11 feb 2020 alle ore 09:12 Szalay-Bekő Máté > > > > >> ha scritto: > > > > >>> > > > > >>> Hi All, > > > > >>> > > > > >>> about the question from Michael: > > > > Regarding the fix, can we just make 3.6.0 aware of the old > > protocol > > > and > > > > speak old message format when it's talking to old server? > > > > >>> > > > > >>> In this particular case, it might be enough. The protocol change > > > happened > > > > >>> now in the 'initial message' sent by the QuorumCnxManager. Maybe > it > > > is > > > > >> not > > > > >>> a problem if the new servers can not initiate channels to the old > > > > >> servers, > > > > >>> maybe it is enough if these channel gets initiated by the old > > servers > > > > >> only. > > > > >>> I will test it quickly. > > > > >>> > > > > >>> Although I have no idea if any other thing changed in the quorum > > > protocol > > > > >>> between 3.5 and 3.6. In other cases it might not be enough if the > > new > > > > >>> servers can understand the old messages, as the old servers can > > > break by > > > > >>> not understanding the messages from the new servers. Also, in the > > > code > > > > >>> currently (AFAIK) there is no generic knowledge of protocol > > > versions, the > > > > >>> servers are not storing that which protocol versions they > > can/should > > > use > > > > >> to > > > > >>> communicate to which particular other servers. Maybe we don't > even > > > need > > > > >>> this, but I would feel better if we would have more tests around > > > these > > > > >>> things. > > > > >>> > > > > >>> My suggestion for the long term: > > > > >>> - let's fix this particular issue now with 3.6.0 quickly (I start > > > doing > > >
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
I hate to say it, but I think 3.6.0 should release as is. It is impossible to *reliably* retrofit backwards compatibility / interoperability onto a release that was engineered from the beginning without that goal. Learn the lesson, set goals differently in the future. On Tue, Feb 11, 2020 at 9:41 AM Szalay-Bekő Máté wrote: > FYI: I created these scripts for my local tests: > https://github.com/symat/zk-rolling-upgrade-test > > For the long term I would also add some script that actually monitors the > state of the quorum and also runs continuous traffic, not just 1-2 > smoketests after each restart. But I don't know how important this would > be. > > On Tue, Feb 11, 2020 at 5:25 PM Enrico Olivelli > wrote: > > > Il giorno mar 11 feb 2020 alle ore 17:17 Andor Molnar > > ha scritto: > > > > > > The most obvious one which crosses my mind is that I previously worked > > on: > > > > > > 1) run old version cluster, > > > 2) connect to each node and run smoke tests, > > > 3) restart one node with new code, > > > 4) goto 2) until all nodes are upgraded > > > > > > I think this wouldn’t work in a “unit test”, we probably need a > separate > > Jenkins job and a nice python script to do this. > > > > > > Andor > > > > > > > > > > > > > > > > On 2020. Feb 11., at 16:38, Patrick Hunt wrote: > > > > > > > > Anyone have ideas how we could add testing for upgrade? Obviously > > something > > > > we're missing, esp given it's import. > > > > I will send an email next days with a proposal. > > btw my idea is very like Andor's one > > > > Once we have an automatic environment we can launch from Jenkins > > > > Enrico > > > > > > > > > > > > Patrick > > > > > > > > On Tue, Feb 11, 2020 at 12:40 AM Enrico Olivelli < > eolive...@gmail.com> > > > > wrote: > > > > > > > >> Il giorno mar 11 feb 2020 alle ore 09:12 Szalay-Bekő Máté > > > >> ha scritto: > > > >>> > > > >>> Hi All, > > > >>> > > > >>> about the question from Michael: > > > Regarding the fix, can we just make 3.6.0 aware of the old > protocol > > and > > > speak old message format when it's talking to old server? > > > >>> > > > >>> In this particular case, it might be enough. The protocol change > > happened > > > >>> now in the 'initial message' sent by the QuorumCnxManager. Maybe it > > is > > > >> not > > > >>> a problem if the new servers can not initiate channels to the old > > > >> servers, > > > >>> maybe it is enough if these channel gets initiated by the old > servers > > > >> only. > > > >>> I will test it quickly. > > > >>> > > > >>> Although I have no idea if any other thing changed in the quorum > > protocol > > > >>> between 3.5 and 3.6. In other cases it might not be enough if the > new > > > >>> servers can understand the old messages, as the old servers can > > break by > > > >>> not understanding the messages from the new servers. Also, in the > > code > > > >>> currently (AFAIK) there is no generic knowledge of protocol > > versions, the > > > >>> servers are not storing that which protocol versions they > can/should > > use > > > >> to > > > >>> communicate to which particular other servers. Maybe we don't even > > need > > > >>> this, but I would feel better if we would have more tests around > > these > > > >>> things. > > > >>> > > > >>> My suggestion for the long term: > > > >>> - let's fix this particular issue now with 3.6.0 quickly (I start > > doing > > > >>> this today) > > > >>> - let's do some automation (backed up with jenkins) that will test > a > > > >> whole > > > >>> combinations of different ZooKeeper upgrade paths by making rolling > > > >>> upgrades during some light traffic. Let's have a bit better > > definition > > > >>> about what we expect (e.g. the quorum is up, but some clients can > get > > > >>> disconnected? What will happen to the ephemeral nodes? Do we want > to > > > >>> gracefully close or transfer the user sessions before stopping the > > old > > > >>> server?) and let's see where this broke. Just by checking the > code, I > > > >> don't > > > >>> think the quorum will always be up (e.g. between older 3.4 versions > > and > > > >>> 3.5). > > > >> > > > >> > > > >> I am happy to work on this topic > > > >> > > > >>> - we need to update the Wiki about the working rolling upgrade > paths > > and > > > >>> maybe about workarounds if needed > > > >>> - we might need to do some fixes (adding backward compatible > versions > > > >>> and/or specific parameters that enforce old protocol temporary > > during the > > > >>> rolling upgrade that can be changed later to the new protocol by > > either > > > >>> dynamic reconfig or by rolling restart) > > > >> > > > >> it would be much better on 3.6 code to have some support for > > > >> compatibility with 3.5 servers > > > >> we can't require old code to be forward compatible but we can make > new > > > >> code be compatible to a certain extend with old code. > > > >> If we can achieve this compatibility goal without a flag is better, > > > >> users won't
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
FYI: I created these scripts for my local tests: https://github.com/symat/zk-rolling-upgrade-test For the long term I would also add some script that actually monitors the state of the quorum and also runs continuous traffic, not just 1-2 smoketests after each restart. But I don't know how important this would be. On Tue, Feb 11, 2020 at 5:25 PM Enrico Olivelli wrote: > Il giorno mar 11 feb 2020 alle ore 17:17 Andor Molnar > ha scritto: > > > > The most obvious one which crosses my mind is that I previously worked > on: > > > > 1) run old version cluster, > > 2) connect to each node and run smoke tests, > > 3) restart one node with new code, > > 4) goto 2) until all nodes are upgraded > > > > I think this wouldn’t work in a “unit test”, we probably need a separate > Jenkins job and a nice python script to do this. > > > > Andor > > > > > > > > > > > On 2020. Feb 11., at 16:38, Patrick Hunt wrote: > > > > > > Anyone have ideas how we could add testing for upgrade? Obviously > something > > > we're missing, esp given it's import. > > I will send an email next days with a proposal. > btw my idea is very like Andor's one > > Once we have an automatic environment we can launch from Jenkins > > Enrico > > > > > > > > Patrick > > > > > > On Tue, Feb 11, 2020 at 12:40 AM Enrico Olivelli > > > wrote: > > > > > >> Il giorno mar 11 feb 2020 alle ore 09:12 Szalay-Bekő Máté > > >> ha scritto: > > >>> > > >>> Hi All, > > >>> > > >>> about the question from Michael: > > Regarding the fix, can we just make 3.6.0 aware of the old protocol > and > > speak old message format when it's talking to old server? > > >>> > > >>> In this particular case, it might be enough. The protocol change > happened > > >>> now in the 'initial message' sent by the QuorumCnxManager. Maybe it > is > > >> not > > >>> a problem if the new servers can not initiate channels to the old > > >> servers, > > >>> maybe it is enough if these channel gets initiated by the old servers > > >> only. > > >>> I will test it quickly. > > >>> > > >>> Although I have no idea if any other thing changed in the quorum > protocol > > >>> between 3.5 and 3.6. In other cases it might not be enough if the new > > >>> servers can understand the old messages, as the old servers can > break by > > >>> not understanding the messages from the new servers. Also, in the > code > > >>> currently (AFAIK) there is no generic knowledge of protocol > versions, the > > >>> servers are not storing that which protocol versions they can/should > use > > >> to > > >>> communicate to which particular other servers. Maybe we don't even > need > > >>> this, but I would feel better if we would have more tests around > these > > >>> things. > > >>> > > >>> My suggestion for the long term: > > >>> - let's fix this particular issue now with 3.6.0 quickly (I start > doing > > >>> this today) > > >>> - let's do some automation (backed up with jenkins) that will test a > > >> whole > > >>> combinations of different ZooKeeper upgrade paths by making rolling > > >>> upgrades during some light traffic. Let's have a bit better > definition > > >>> about what we expect (e.g. the quorum is up, but some clients can get > > >>> disconnected? What will happen to the ephemeral nodes? Do we want to > > >>> gracefully close or transfer the user sessions before stopping the > old > > >>> server?) and let's see where this broke. Just by checking the code, I > > >> don't > > >>> think the quorum will always be up (e.g. between older 3.4 versions > and > > >>> 3.5). > > >> > > >> > > >> I am happy to work on this topic > > >> > > >>> - we need to update the Wiki about the working rolling upgrade paths > and > > >>> maybe about workarounds if needed > > >>> - we might need to do some fixes (adding backward compatible versions > > >>> and/or specific parameters that enforce old protocol temporary > during the > > >>> rolling upgrade that can be changed later to the new protocol by > either > > >>> dynamic reconfig or by rolling restart) > > >> > > >> it would be much better on 3.6 code to have some support for > > >> compatibility with 3.5 servers > > >> we can't require old code to be forward compatible but we can make new > > >> code be compatible to a certain extend with old code. > > >> If we can achieve this compatibility goal without a flag is better, > > >> users won't have to care about this part and they simply "trust" on us > > >> > > >> The rollback story is also important, but maybe we are still not ready > > >> for it, in case of local changes to store, > > >> it is better to have a clear design and plan and work for a new > release > > >> (3.7?) > > >> > > >> Enrico > > >> > > >>> > > >>> Depending on your comments, I am happy to create a few Jira tickets > > >> around > > >>> these topics. > > >>> > > >>> Kind regards, > > >>> Mate > > >>> > > >>> ps. Enrico, sorry about your RC... I owe you a beer, let me know if > you > > >> are > > >>> near to Budapest ;) > > >>> > > >>> On Tue,
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Il giorno mar 11 feb 2020 alle ore 17:17 Andor Molnar ha scritto: > > The most obvious one which crosses my mind is that I previously worked on: > > 1) run old version cluster, > 2) connect to each node and run smoke tests, > 3) restart one node with new code, > 4) goto 2) until all nodes are upgraded > > I think this wouldn’t work in a “unit test”, we probably need a separate > Jenkins job and a nice python script to do this. > > Andor > > > > > > On 2020. Feb 11., at 16:38, Patrick Hunt wrote: > > > > Anyone have ideas how we could add testing for upgrade? Obviously something > > we're missing, esp given it's import. I will send an email next days with a proposal. btw my idea is very like Andor's one Once we have an automatic environment we can launch from Jenkins Enrico > > > > Patrick > > > > On Tue, Feb 11, 2020 at 12:40 AM Enrico Olivelli > > wrote: > > > >> Il giorno mar 11 feb 2020 alle ore 09:12 Szalay-Bekő Máté > >> ha scritto: > >>> > >>> Hi All, > >>> > >>> about the question from Michael: > Regarding the fix, can we just make 3.6.0 aware of the old protocol and > speak old message format when it's talking to old server? > >>> > >>> In this particular case, it might be enough. The protocol change happened > >>> now in the 'initial message' sent by the QuorumCnxManager. Maybe it is > >> not > >>> a problem if the new servers can not initiate channels to the old > >> servers, > >>> maybe it is enough if these channel gets initiated by the old servers > >> only. > >>> I will test it quickly. > >>> > >>> Although I have no idea if any other thing changed in the quorum protocol > >>> between 3.5 and 3.6. In other cases it might not be enough if the new > >>> servers can understand the old messages, as the old servers can break by > >>> not understanding the messages from the new servers. Also, in the code > >>> currently (AFAIK) there is no generic knowledge of protocol versions, the > >>> servers are not storing that which protocol versions they can/should use > >> to > >>> communicate to which particular other servers. Maybe we don't even need > >>> this, but I would feel better if we would have more tests around these > >>> things. > >>> > >>> My suggestion for the long term: > >>> - let's fix this particular issue now with 3.6.0 quickly (I start doing > >>> this today) > >>> - let's do some automation (backed up with jenkins) that will test a > >> whole > >>> combinations of different ZooKeeper upgrade paths by making rolling > >>> upgrades during some light traffic. Let's have a bit better definition > >>> about what we expect (e.g. the quorum is up, but some clients can get > >>> disconnected? What will happen to the ephemeral nodes? Do we want to > >>> gracefully close or transfer the user sessions before stopping the old > >>> server?) and let's see where this broke. Just by checking the code, I > >> don't > >>> think the quorum will always be up (e.g. between older 3.4 versions and > >>> 3.5). > >> > >> > >> I am happy to work on this topic > >> > >>> - we need to update the Wiki about the working rolling upgrade paths and > >>> maybe about workarounds if needed > >>> - we might need to do some fixes (adding backward compatible versions > >>> and/or specific parameters that enforce old protocol temporary during the > >>> rolling upgrade that can be changed later to the new protocol by either > >>> dynamic reconfig or by rolling restart) > >> > >> it would be much better on 3.6 code to have some support for > >> compatibility with 3.5 servers > >> we can't require old code to be forward compatible but we can make new > >> code be compatible to a certain extend with old code. > >> If we can achieve this compatibility goal without a flag is better, > >> users won't have to care about this part and they simply "trust" on us > >> > >> The rollback story is also important, but maybe we are still not ready > >> for it, in case of local changes to store, > >> it is better to have a clear design and plan and work for a new release > >> (3.7?) > >> > >> Enrico > >> > >>> > >>> Depending on your comments, I am happy to create a few Jira tickets > >> around > >>> these topics. > >>> > >>> Kind regards, > >>> Mate > >>> > >>> ps. Enrico, sorry about your RC... I owe you a beer, let me know if you > >> are > >>> near to Budapest ;) > >>> > >>> On Tue, Feb 11, 2020 at 8:43 AM Enrico Olivelli > >> wrote: > >>> > Good. > > I will cancel the vote for 3.6.0rc2. > > I appreciate very much If Mate and his colleagues have time to work on > >> a > fix. > Otherwise I will have cycles next week > > I would also like to spend my time in setting up a few minimal > >> integration > tests about the upgrade story > > Enrico > > Il Mar 11 Feb 2020, 07:30 Michael Han ha scritto: > > > Kudos Enrico, very thorough work as the final gate keeper of the > >> release! > > > > Now with this, I'd like to *vote a -1* on
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
The most obvious one which crosses my mind is that I previously worked on: 1) run old version cluster, 2) connect to each node and run smoke tests, 3) restart one node with new code, 4) goto 2) until all nodes are upgraded I think this wouldn’t work in a “unit test”, we probably need a separate Jenkins job and a nice python script to do this. Andor > On 2020. Feb 11., at 16:38, Patrick Hunt wrote: > > Anyone have ideas how we could add testing for upgrade? Obviously something > we're missing, esp given it's import. > > Patrick > > On Tue, Feb 11, 2020 at 12:40 AM Enrico Olivelli > wrote: > >> Il giorno mar 11 feb 2020 alle ore 09:12 Szalay-Bekő Máté >> ha scritto: >>> >>> Hi All, >>> >>> about the question from Michael: Regarding the fix, can we just make 3.6.0 aware of the old protocol and speak old message format when it's talking to old server? >>> >>> In this particular case, it might be enough. The protocol change happened >>> now in the 'initial message' sent by the QuorumCnxManager. Maybe it is >> not >>> a problem if the new servers can not initiate channels to the old >> servers, >>> maybe it is enough if these channel gets initiated by the old servers >> only. >>> I will test it quickly. >>> >>> Although I have no idea if any other thing changed in the quorum protocol >>> between 3.5 and 3.6. In other cases it might not be enough if the new >>> servers can understand the old messages, as the old servers can break by >>> not understanding the messages from the new servers. Also, in the code >>> currently (AFAIK) there is no generic knowledge of protocol versions, the >>> servers are not storing that which protocol versions they can/should use >> to >>> communicate to which particular other servers. Maybe we don't even need >>> this, but I would feel better if we would have more tests around these >>> things. >>> >>> My suggestion for the long term: >>> - let's fix this particular issue now with 3.6.0 quickly (I start doing >>> this today) >>> - let's do some automation (backed up with jenkins) that will test a >> whole >>> combinations of different ZooKeeper upgrade paths by making rolling >>> upgrades during some light traffic. Let's have a bit better definition >>> about what we expect (e.g. the quorum is up, but some clients can get >>> disconnected? What will happen to the ephemeral nodes? Do we want to >>> gracefully close or transfer the user sessions before stopping the old >>> server?) and let's see where this broke. Just by checking the code, I >> don't >>> think the quorum will always be up (e.g. between older 3.4 versions and >>> 3.5). >> >> >> I am happy to work on this topic >> >>> - we need to update the Wiki about the working rolling upgrade paths and >>> maybe about workarounds if needed >>> - we might need to do some fixes (adding backward compatible versions >>> and/or specific parameters that enforce old protocol temporary during the >>> rolling upgrade that can be changed later to the new protocol by either >>> dynamic reconfig or by rolling restart) >> >> it would be much better on 3.6 code to have some support for >> compatibility with 3.5 servers >> we can't require old code to be forward compatible but we can make new >> code be compatible to a certain extend with old code. >> If we can achieve this compatibility goal without a flag is better, >> users won't have to care about this part and they simply "trust" on us >> >> The rollback story is also important, but maybe we are still not ready >> for it, in case of local changes to store, >> it is better to have a clear design and plan and work for a new release >> (3.7?) >> >> Enrico >> >>> >>> Depending on your comments, I am happy to create a few Jira tickets >> around >>> these topics. >>> >>> Kind regards, >>> Mate >>> >>> ps. Enrico, sorry about your RC... I owe you a beer, let me know if you >> are >>> near to Budapest ;) >>> >>> On Tue, Feb 11, 2020 at 8:43 AM Enrico Olivelli >> wrote: >>> Good. I will cancel the vote for 3.6.0rc2. I appreciate very much If Mate and his colleagues have time to work on >> a fix. Otherwise I will have cycles next week I would also like to spend my time in setting up a few minimal >> integration tests about the upgrade story Enrico Il Mar 11 Feb 2020, 07:30 Michael Han ha scritto: > Kudos Enrico, very thorough work as the final gate keeper of the >> release! > > Now with this, I'd like to *vote a -1* on the 3.6.0 RC2. > > I'd recommend we fix this issue for 3.6.0. ZooKeeper is one of the >> rare > piece of software that put so much emphasis on compatibilities thus >> it just > works when upgrade / downgrade, which is amazing. One guarantee we >> always > had is during rolling upgrade, the quorum will always be available, leading > to no service interruption. It would be sad we lose such capability >> given > this
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Anyone have ideas how we could add testing for upgrade? Obviously something we're missing, esp given it's import. Patrick On Tue, Feb 11, 2020 at 12:40 AM Enrico Olivelli wrote: > Il giorno mar 11 feb 2020 alle ore 09:12 Szalay-Bekő Máté > ha scritto: > > > > Hi All, > > > > about the question from Michael: > > > Regarding the fix, can we just make 3.6.0 aware of the old protocol and > > > speak old message format when it's talking to old server? > > > > In this particular case, it might be enough. The protocol change happened > > now in the 'initial message' sent by the QuorumCnxManager. Maybe it is > not > > a problem if the new servers can not initiate channels to the old > servers, > > maybe it is enough if these channel gets initiated by the old servers > only. > > I will test it quickly. > > > > Although I have no idea if any other thing changed in the quorum protocol > > between 3.5 and 3.6. In other cases it might not be enough if the new > > servers can understand the old messages, as the old servers can break by > > not understanding the messages from the new servers. Also, in the code > > currently (AFAIK) there is no generic knowledge of protocol versions, the > > servers are not storing that which protocol versions they can/should use > to > > communicate to which particular other servers. Maybe we don't even need > > this, but I would feel better if we would have more tests around these > > things. > > > > My suggestion for the long term: > > - let's fix this particular issue now with 3.6.0 quickly (I start doing > > this today) > > - let's do some automation (backed up with jenkins) that will test a > whole > > combinations of different ZooKeeper upgrade paths by making rolling > > upgrades during some light traffic. Let's have a bit better definition > > about what we expect (e.g. the quorum is up, but some clients can get > > disconnected? What will happen to the ephemeral nodes? Do we want to > > gracefully close or transfer the user sessions before stopping the old > > server?) and let's see where this broke. Just by checking the code, I > don't > > think the quorum will always be up (e.g. between older 3.4 versions and > > 3.5). > > > I am happy to work on this topic > > > - we need to update the Wiki about the working rolling upgrade paths and > > maybe about workarounds if needed > > - we might need to do some fixes (adding backward compatible versions > > and/or specific parameters that enforce old protocol temporary during the > > rolling upgrade that can be changed later to the new protocol by either > > dynamic reconfig or by rolling restart) > > it would be much better on 3.6 code to have some support for > compatibility with 3.5 servers > we can't require old code to be forward compatible but we can make new > code be compatible to a certain extend with old code. > If we can achieve this compatibility goal without a flag is better, > users won't have to care about this part and they simply "trust" on us > > The rollback story is also important, but maybe we are still not ready > for it, in case of local changes to store, > it is better to have a clear design and plan and work for a new release > (3.7?) > > Enrico > > > > > Depending on your comments, I am happy to create a few Jira tickets > around > > these topics. > > > > Kind regards, > > Mate > > > > ps. Enrico, sorry about your RC... I owe you a beer, let me know if you > are > > near to Budapest ;) > > > > On Tue, Feb 11, 2020 at 8:43 AM Enrico Olivelli > wrote: > > > > > Good. > > > > > > I will cancel the vote for 3.6.0rc2. > > > > > > I appreciate very much If Mate and his colleagues have time to work on > a > > > fix. > > > Otherwise I will have cycles next week > > > > > > I would also like to spend my time in setting up a few minimal > integration > > > tests about the upgrade story > > > > > > Enrico > > > > > > Il Mar 11 Feb 2020, 07:30 Michael Han ha scritto: > > > > > > > Kudos Enrico, very thorough work as the final gate keeper of the > release! > > > > > > > > Now with this, I'd like to *vote a -1* on the 3.6.0 RC2. > > > > > > > > I'd recommend we fix this issue for 3.6.0. ZooKeeper is one of the > rare > > > > piece of software that put so much emphasis on compatibilities thus > it > > > just > > > > works when upgrade / downgrade, which is amazing. One guarantee we > always > > > > had is during rolling upgrade, the quorum will always be available, > > > leading > > > > to no service interruption. It would be sad we lose such capability > given > > > > this is still a tractable problem. > > > > > > > > Regarding the fix, can we just make 3.6.0 aware of the old protocol > and > > > > speak old message format when it's talking to old server? Basically, > an > > > > ugly if else check against the protocol version should work and > there is > > > no > > > > need to have multiple pass on rolling upgrade process. > > > > > > > > > > > > On Mon, Feb 10, 2020 at 10:23 PM Enrico Olivelli < >
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Il giorno mar 11 feb 2020 alle ore 09:12 Szalay-Bekő Máté ha scritto: > > Hi All, > > about the question from Michael: > > Regarding the fix, can we just make 3.6.0 aware of the old protocol and > > speak old message format when it's talking to old server? > > In this particular case, it might be enough. The protocol change happened > now in the 'initial message' sent by the QuorumCnxManager. Maybe it is not > a problem if the new servers can not initiate channels to the old servers, > maybe it is enough if these channel gets initiated by the old servers only. > I will test it quickly. > > Although I have no idea if any other thing changed in the quorum protocol > between 3.5 and 3.6. In other cases it might not be enough if the new > servers can understand the old messages, as the old servers can break by > not understanding the messages from the new servers. Also, in the code > currently (AFAIK) there is no generic knowledge of protocol versions, the > servers are not storing that which protocol versions they can/should use to > communicate to which particular other servers. Maybe we don't even need > this, but I would feel better if we would have more tests around these > things. > > My suggestion for the long term: > - let's fix this particular issue now with 3.6.0 quickly (I start doing > this today) > - let's do some automation (backed up with jenkins) that will test a whole > combinations of different ZooKeeper upgrade paths by making rolling > upgrades during some light traffic. Let's have a bit better definition > about what we expect (e.g. the quorum is up, but some clients can get > disconnected? What will happen to the ephemeral nodes? Do we want to > gracefully close or transfer the user sessions before stopping the old > server?) and let's see where this broke. Just by checking the code, I don't > think the quorum will always be up (e.g. between older 3.4 versions and > 3.5). I am happy to work on this topic > - we need to update the Wiki about the working rolling upgrade paths and > maybe about workarounds if needed > - we might need to do some fixes (adding backward compatible versions > and/or specific parameters that enforce old protocol temporary during the > rolling upgrade that can be changed later to the new protocol by either > dynamic reconfig or by rolling restart) it would be much better on 3.6 code to have some support for compatibility with 3.5 servers we can't require old code to be forward compatible but we can make new code be compatible to a certain extend with old code. If we can achieve this compatibility goal without a flag is better, users won't have to care about this part and they simply "trust" on us The rollback story is also important, but maybe we are still not ready for it, in case of local changes to store, it is better to have a clear design and plan and work for a new release (3.7?) Enrico > > Depending on your comments, I am happy to create a few Jira tickets around > these topics. > > Kind regards, > Mate > > ps. Enrico, sorry about your RC... I owe you a beer, let me know if you are > near to Budapest ;) > > On Tue, Feb 11, 2020 at 8:43 AM Enrico Olivelli wrote: > > > Good. > > > > I will cancel the vote for 3.6.0rc2. > > > > I appreciate very much If Mate and his colleagues have time to work on a > > fix. > > Otherwise I will have cycles next week > > > > I would also like to spend my time in setting up a few minimal integration > > tests about the upgrade story > > > > Enrico > > > > Il Mar 11 Feb 2020, 07:30 Michael Han ha scritto: > > > > > Kudos Enrico, very thorough work as the final gate keeper of the release! > > > > > > Now with this, I'd like to *vote a -1* on the 3.6.0 RC2. > > > > > > I'd recommend we fix this issue for 3.6.0. ZooKeeper is one of the rare > > > piece of software that put so much emphasis on compatibilities thus it > > just > > > works when upgrade / downgrade, which is amazing. One guarantee we always > > > had is during rolling upgrade, the quorum will always be available, > > leading > > > to no service interruption. It would be sad we lose such capability given > > > this is still a tractable problem. > > > > > > Regarding the fix, can we just make 3.6.0 aware of the old protocol and > > > speak old message format when it's talking to old server? Basically, an > > > ugly if else check against the protocol version should work and there is > > no > > > need to have multiple pass on rolling upgrade process. > > > > > > > > > On Mon, Feb 10, 2020 at 10:23 PM Enrico Olivelli > > > wrote: > > > > > > > I suggest this plan: > > > > - release 3.6.0 now > > > > - improve the migration story, the flow outlined by Mate is > > > > interesting, but it will take time > > > > > > > > 3.6.0rc2 got enough binding votes so I am going to finalize the > > > > release this evening (within 8-10 hours) if no one comes out in the > > > > VOTE thread with a -1 > > > > > > > > Enrico > > > > > > > > Enrico > > > > > > > > Il giorno lun 10
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Hi All, about the question from Michael: > Regarding the fix, can we just make 3.6.0 aware of the old protocol and > speak old message format when it's talking to old server? In this particular case, it might be enough. The protocol change happened now in the 'initial message' sent by the QuorumCnxManager. Maybe it is not a problem if the new servers can not initiate channels to the old servers, maybe it is enough if these channel gets initiated by the old servers only. I will test it quickly. Although I have no idea if any other thing changed in the quorum protocol between 3.5 and 3.6. In other cases it might not be enough if the new servers can understand the old messages, as the old servers can break by not understanding the messages from the new servers. Also, in the code currently (AFAIK) there is no generic knowledge of protocol versions, the servers are not storing that which protocol versions they can/should use to communicate to which particular other servers. Maybe we don't even need this, but I would feel better if we would have more tests around these things. My suggestion for the long term: - let's fix this particular issue now with 3.6.0 quickly (I start doing this today) - let's do some automation (backed up with jenkins) that will test a whole combinations of different ZooKeeper upgrade paths by making rolling upgrades during some light traffic. Let's have a bit better definition about what we expect (e.g. the quorum is up, but some clients can get disconnected? What will happen to the ephemeral nodes? Do we want to gracefully close or transfer the user sessions before stopping the old server?) and let's see where this broke. Just by checking the code, I don't think the quorum will always be up (e.g. between older 3.4 versions and 3.5). - we need to update the Wiki about the working rolling upgrade paths and maybe about workarounds if needed - we might need to do some fixes (adding backward compatible versions and/or specific parameters that enforce old protocol temporary during the rolling upgrade that can be changed later to the new protocol by either dynamic reconfig or by rolling restart) Depending on your comments, I am happy to create a few Jira tickets around these topics. Kind regards, Mate ps. Enrico, sorry about your RC... I owe you a beer, let me know if you are near to Budapest ;) On Tue, Feb 11, 2020 at 8:43 AM Enrico Olivelli wrote: > Good. > > I will cancel the vote for 3.6.0rc2. > > I appreciate very much If Mate and his colleagues have time to work on a > fix. > Otherwise I will have cycles next week > > I would also like to spend my time in setting up a few minimal integration > tests about the upgrade story > > Enrico > > Il Mar 11 Feb 2020, 07:30 Michael Han ha scritto: > > > Kudos Enrico, very thorough work as the final gate keeper of the release! > > > > Now with this, I'd like to *vote a -1* on the 3.6.0 RC2. > > > > I'd recommend we fix this issue for 3.6.0. ZooKeeper is one of the rare > > piece of software that put so much emphasis on compatibilities thus it > just > > works when upgrade / downgrade, which is amazing. One guarantee we always > > had is during rolling upgrade, the quorum will always be available, > leading > > to no service interruption. It would be sad we lose such capability given > > this is still a tractable problem. > > > > Regarding the fix, can we just make 3.6.0 aware of the old protocol and > > speak old message format when it's talking to old server? Basically, an > > ugly if else check against the protocol version should work and there is > no > > need to have multiple pass on rolling upgrade process. > > > > > > On Mon, Feb 10, 2020 at 10:23 PM Enrico Olivelli > > wrote: > > > > > I suggest this plan: > > > - release 3.6.0 now > > > - improve the migration story, the flow outlined by Mate is > > > interesting, but it will take time > > > > > > 3.6.0rc2 got enough binding votes so I am going to finalize the > > > release this evening (within 8-10 hours) if no one comes out in the > > > VOTE thread with a -1 > > > > > > Enrico > > > > > > Enrico > > > > > > Il giorno lun 10 feb 2020 alle ore 19:33 Patrick Hunt > > > ha scritto: > > > > > > > > On Mon, Feb 10, 2020 at 3:38 AM Andor Molnar > wrote: > > > > > > > > > Hi, > > > > > > > > > > Answers inline. > > > > > > > > > > > > > > > > In my experience when you are close to a release it is better to > to > > > > > > make big changes. (I am among the approvers of that patch, so I > am > > > > > > responsible for this change) > > > > > > > > > > > > > > > > > > > > Although this statement is acceptable for me, I don’t feel this > patch > > > > > should not have been merged into 3.6.0. Submission has been > preceded > > > by a > > > > > long argument with MAPR folks who originally wanted to be merged > into > > > 3.4 > > > > > branch (considering the pace how ZooKeeper community is moving > > > forward) and > > > > > we reached an agreement that release it with 3.6.0. > > > > >
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Good. I will cancel the vote for 3.6.0rc2. I appreciate very much If Mate and his colleagues have time to work on a fix. Otherwise I will have cycles next week I would also like to spend my time in setting up a few minimal integration tests about the upgrade story Enrico Il Mar 11 Feb 2020, 07:30 Michael Han ha scritto: > Kudos Enrico, very thorough work as the final gate keeper of the release! > > Now with this, I'd like to *vote a -1* on the 3.6.0 RC2. > > I'd recommend we fix this issue for 3.6.0. ZooKeeper is one of the rare > piece of software that put so much emphasis on compatibilities thus it just > works when upgrade / downgrade, which is amazing. One guarantee we always > had is during rolling upgrade, the quorum will always be available, leading > to no service interruption. It would be sad we lose such capability given > this is still a tractable problem. > > Regarding the fix, can we just make 3.6.0 aware of the old protocol and > speak old message format when it's talking to old server? Basically, an > ugly if else check against the protocol version should work and there is no > need to have multiple pass on rolling upgrade process. > > > On Mon, Feb 10, 2020 at 10:23 PM Enrico Olivelli > wrote: > > > I suggest this plan: > > - release 3.6.0 now > > - improve the migration story, the flow outlined by Mate is > > interesting, but it will take time > > > > 3.6.0rc2 got enough binding votes so I am going to finalize the > > release this evening (within 8-10 hours) if no one comes out in the > > VOTE thread with a -1 > > > > Enrico > > > > Enrico > > > > Il giorno lun 10 feb 2020 alle ore 19:33 Patrick Hunt > > ha scritto: > > > > > > On Mon, Feb 10, 2020 at 3:38 AM Andor Molnar wrote: > > > > > > > Hi, > > > > > > > > Answers inline. > > > > > > > > > > > > > In my experience when you are close to a release it is better to to > > > > > make big changes. (I am among the approvers of that patch, so I am > > > > > responsible for this change) > > > > > > > > > > > > > > > > Although this statement is acceptable for me, I don’t feel this patch > > > > should not have been merged into 3.6.0. Submission has been preceded > > by a > > > > long argument with MAPR folks who originally wanted to be merged into > > 3.4 > > > > branch (considering the pace how ZooKeeper community is moving > > forward) and > > > > we reached an agreement that release it with 3.6.0. > > > > > > > > Make a long story short, this patch has been outstanding for ages > > without > > > > much attention from the community and contributors made a lot of > > effort to > > > > get it done before the release. > > > > > > > > > > > > > I would like to ear from people that have been in the community for > > > > > long time, then I am ready to complete the release process for > > > > > 3.6.0rc2. > > > > > > > > > > > > Me too. > > > > > > > > I tend to accept the way rolling restart works now - as you described > > > > Enrico - and given that situation was pretty much the same between > 3.4 > > and > > > > 3.5, I don’t feel we have to make additional changes. > > > > > > > > On the other hand, the fix that Mate suggested sounds quite cool, I’m > > also > > > > happy to work on getting it in. > > > > > > > > Fyi, Release Management page says the following: > > > > > > https://cwiki.apache.org/confluence/display/ZOOKEEPER/ReleaseManagement > > > > > > > > "major.minor release of ZooKeeper must be backwards compatible with > the > > > > previous minor release, major.(minor-1)" > > > > > > > > > > > Our users, direct and indirect, value the ability to migrate to newer > > > versions - esp as we drop support for older. Frictions such as this can > > be > > > a reason to go elsewhere. I'm "pro" b/w compact - esp given our > published > > > guidelines. > > > > > > Patrick > > > > > > > > > > Andor > > > > > > > > > > > > > > > > > > > > > On 2020. Feb 10., at 11:32, Enrico Olivelli > > wrote: > > > > > > > > > > Thank you Mate for checking and explaining this story. > > > > > > > > > > I find it very interesting that the cause is ZOOKEEPER-3188 as: > > > > > - it is the last "big patch" committed to 3.6 before starting the > > > > > release process > > > > > - it is the cause of the failure of the first RC > > > > > > > > > > In my experience when you are close to a release it is better to to > > > > > make big changes. (I am among the approvers of that patch, so I am > > > > > responsible for this change) > > > > > > > > > > This is a pointer to the change to whom who wants to understand > > better > > > > > the context > > > > > > > > > > > > https://github.com/apache/zookeeper/pull/1048/files#diff-7a209d890686bcba351d758b64b22a7dR11 > > > > > > > > > > IIUC even for the upgrade from 3.4 to 3.5 the story was the same > and > > > > > if this statement holds then I feel we can continue > > > > > with this release. > > > > > > > > > > - Reverting ZOOKEEPER-3188 is not an option for me, it is too > > complex. > > > > > - Making 3.5
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Kudos Enrico, very thorough work as the final gate keeper of the release! Now with this, I'd like to *vote a -1* on the 3.6.0 RC2. I'd recommend we fix this issue for 3.6.0. ZooKeeper is one of the rare piece of software that put so much emphasis on compatibilities thus it just works when upgrade / downgrade, which is amazing. One guarantee we always had is during rolling upgrade, the quorum will always be available, leading to no service interruption. It would be sad we lose such capability given this is still a tractable problem. Regarding the fix, can we just make 3.6.0 aware of the old protocol and speak old message format when it's talking to old server? Basically, an ugly if else check against the protocol version should work and there is no need to have multiple pass on rolling upgrade process. On Mon, Feb 10, 2020 at 10:23 PM Enrico Olivelli wrote: > I suggest this plan: > - release 3.6.0 now > - improve the migration story, the flow outlined by Mate is > interesting, but it will take time > > 3.6.0rc2 got enough binding votes so I am going to finalize the > release this evening (within 8-10 hours) if no one comes out in the > VOTE thread with a -1 > > Enrico > > Enrico > > Il giorno lun 10 feb 2020 alle ore 19:33 Patrick Hunt > ha scritto: > > > > On Mon, Feb 10, 2020 at 3:38 AM Andor Molnar wrote: > > > > > Hi, > > > > > > Answers inline. > > > > > > > > > > In my experience when you are close to a release it is better to to > > > > make big changes. (I am among the approvers of that patch, so I am > > > > responsible for this change) > > > > > > > > > > > > Although this statement is acceptable for me, I don’t feel this patch > > > should not have been merged into 3.6.0. Submission has been preceded > by a > > > long argument with MAPR folks who originally wanted to be merged into > 3.4 > > > branch (considering the pace how ZooKeeper community is moving > forward) and > > > we reached an agreement that release it with 3.6.0. > > > > > > Make a long story short, this patch has been outstanding for ages > without > > > much attention from the community and contributors made a lot of > effort to > > > get it done before the release. > > > > > > > > > > I would like to ear from people that have been in the community for > > > > long time, then I am ready to complete the release process for > > > > 3.6.0rc2. > > > > > > > > > Me too. > > > > > > I tend to accept the way rolling restart works now - as you described > > > Enrico - and given that situation was pretty much the same between 3.4 > and > > > 3.5, I don’t feel we have to make additional changes. > > > > > > On the other hand, the fix that Mate suggested sounds quite cool, I’m > also > > > happy to work on getting it in. > > > > > > Fyi, Release Management page says the following: > > > > https://cwiki.apache.org/confluence/display/ZOOKEEPER/ReleaseManagement > > > > > > "major.minor release of ZooKeeper must be backwards compatible with the > > > previous minor release, major.(minor-1)" > > > > > > > > Our users, direct and indirect, value the ability to migrate to newer > > versions - esp as we drop support for older. Frictions such as this can > be > > a reason to go elsewhere. I'm "pro" b/w compact - esp given our published > > guidelines. > > > > Patrick > > > > > > > Andor > > > > > > > > > > > > > > > > On 2020. Feb 10., at 11:32, Enrico Olivelli > wrote: > > > > > > > > Thank you Mate for checking and explaining this story. > > > > > > > > I find it very interesting that the cause is ZOOKEEPER-3188 as: > > > > - it is the last "big patch" committed to 3.6 before starting the > > > > release process > > > > - it is the cause of the failure of the first RC > > > > > > > > In my experience when you are close to a release it is better to to > > > > make big changes. (I am among the approvers of that patch, so I am > > > > responsible for this change) > > > > > > > > This is a pointer to the change to whom who wants to understand > better > > > > the context > > > > > > > > https://github.com/apache/zookeeper/pull/1048/files#diff-7a209d890686bcba351d758b64b22a7dR11 > > > > > > > > IIUC even for the upgrade from 3.4 to 3.5 the story was the same and > > > > if this statement holds then I feel we can continue > > > > with this release. > > > > > > > > - Reverting ZOOKEEPER-3188 is not an option for me, it is too > complex. > > > > - Making 3.5 and 3.6 "compatible" can be very tricky and we do not > > > > have tools to certify this compatibility (at least not in the short > > > > term) > > > > > > > > I would like to ear from people that have been in the community for > > > > long time, then I am ready to complete the release process for > > > > 3.6.0rc2. > > > > > > > > I will update the website and the release notes with a specific > > > > warning about the upgrade, we should also update the Wiki > > > > > > > > Enrico > > > > > > > > > > > > Il giorno lun 10 feb 2020 alle ore 11:17 Szalay-Bekő Máté > > > > ha scritto: > > > >>
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
I suggest this plan: - release 3.6.0 now - improve the migration story, the flow outlined by Mate is interesting, but it will take time 3.6.0rc2 got enough binding votes so I am going to finalize the release this evening (within 8-10 hours) if no one comes out in the VOTE thread with a -1 Enrico Enrico Il giorno lun 10 feb 2020 alle ore 19:33 Patrick Hunt ha scritto: > > On Mon, Feb 10, 2020 at 3:38 AM Andor Molnar wrote: > > > Hi, > > > > Answers inline. > > > > > > > In my experience when you are close to a release it is better to to > > > make big changes. (I am among the approvers of that patch, so I am > > > responsible for this change) > > > > > > > > Although this statement is acceptable for me, I don’t feel this patch > > should not have been merged into 3.6.0. Submission has been preceded by a > > long argument with MAPR folks who originally wanted to be merged into 3.4 > > branch (considering the pace how ZooKeeper community is moving forward) and > > we reached an agreement that release it with 3.6.0. > > > > Make a long story short, this patch has been outstanding for ages without > > much attention from the community and contributors made a lot of effort to > > get it done before the release. > > > > > > > I would like to ear from people that have been in the community for > > > long time, then I am ready to complete the release process for > > > 3.6.0rc2. > > > > > > Me too. > > > > I tend to accept the way rolling restart works now - as you described > > Enrico - and given that situation was pretty much the same between 3.4 and > > 3.5, I don’t feel we have to make additional changes. > > > > On the other hand, the fix that Mate suggested sounds quite cool, I’m also > > happy to work on getting it in. > > > > Fyi, Release Management page says the following: > > https://cwiki.apache.org/confluence/display/ZOOKEEPER/ReleaseManagement > > > > "major.minor release of ZooKeeper must be backwards compatible with the > > previous minor release, major.(minor-1)" > > > > > Our users, direct and indirect, value the ability to migrate to newer > versions - esp as we drop support for older. Frictions such as this can be > a reason to go elsewhere. I'm "pro" b/w compact - esp given our published > guidelines. > > Patrick > > > > Andor > > > > > > > > > > > On 2020. Feb 10., at 11:32, Enrico Olivelli wrote: > > > > > > Thank you Mate for checking and explaining this story. > > > > > > I find it very interesting that the cause is ZOOKEEPER-3188 as: > > > - it is the last "big patch" committed to 3.6 before starting the > > > release process > > > - it is the cause of the failure of the first RC > > > > > > In my experience when you are close to a release it is better to to > > > make big changes. (I am among the approvers of that patch, so I am > > > responsible for this change) > > > > > > This is a pointer to the change to whom who wants to understand better > > > the context > > > > > https://github.com/apache/zookeeper/pull/1048/files#diff-7a209d890686bcba351d758b64b22a7dR11 > > > > > > IIUC even for the upgrade from 3.4 to 3.5 the story was the same and > > > if this statement holds then I feel we can continue > > > with this release. > > > > > > - Reverting ZOOKEEPER-3188 is not an option for me, it is too complex. > > > - Making 3.5 and 3.6 "compatible" can be very tricky and we do not > > > have tools to certify this compatibility (at least not in the short > > > term) > > > > > > I would like to ear from people that have been in the community for > > > long time, then I am ready to complete the release process for > > > 3.6.0rc2. > > > > > > I will update the website and the release notes with a specific > > > warning about the upgrade, we should also update the Wiki > > > > > > Enrico > > > > > > > > > Il giorno lun 10 feb 2020 alle ore 11:17 Szalay-Bekő Máté > > > ha scritto: > > >> > > >> Hi Enrico! > > >> > > >> This is caused by the different PROTOCOL_VERSION in the > > QuorumCnxManager. > > >> The Protocol version was changed last time in ZOOKEEPER-2186 released > > >> first in 3.4.7 and 3.5.1 to avoid some crashing / fix some bugs. Later I > > >> also changed the protocol version when the format of the initial message > > >> changed in ZOOKEEPER-3188. So actually the quorum protocol is not > > >> compatible in this case and is the 'expected' behavior if you upgrade > > e.g > > >> from 3.4.6 to 3.4.7, or 3.4.6 to 3.5.5 or e.g from 3.5.6 to 3.6.0. > > >> > > >> We had some discussion in the PR of ZOOKEEPER-3188 back then and got to > > the > > >> conclusion that it is not that bad, as there will be no data loss as you > > >> wrote. The tricky thing is that during rolling upgrade we should ensure > > >> both backward and forward compatibility to make sure that the old and > > the > > >> new part of the quorum can still speak to each other. The current > > solution > > >> (simply failing if the protocol versions mismatch) is more simple and > > still > > >> working just fine: as the
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
On Mon, Feb 10, 2020 at 3:38 AM Andor Molnar wrote: > Hi, > > Answers inline. > > > > In my experience when you are close to a release it is better to to > > make big changes. (I am among the approvers of that patch, so I am > > responsible for this change) > > > > Although this statement is acceptable for me, I don’t feel this patch > should not have been merged into 3.6.0. Submission has been preceded by a > long argument with MAPR folks who originally wanted to be merged into 3.4 > branch (considering the pace how ZooKeeper community is moving forward) and > we reached an agreement that release it with 3.6.0. > > Make a long story short, this patch has been outstanding for ages without > much attention from the community and contributors made a lot of effort to > get it done before the release. > > > > I would like to ear from people that have been in the community for > > long time, then I am ready to complete the release process for > > 3.6.0rc2. > > > Me too. > > I tend to accept the way rolling restart works now - as you described > Enrico - and given that situation was pretty much the same between 3.4 and > 3.5, I don’t feel we have to make additional changes. > > On the other hand, the fix that Mate suggested sounds quite cool, I’m also > happy to work on getting it in. > > Fyi, Release Management page says the following: > https://cwiki.apache.org/confluence/display/ZOOKEEPER/ReleaseManagement > > "major.minor release of ZooKeeper must be backwards compatible with the > previous minor release, major.(minor-1)" > > Our users, direct and indirect, value the ability to migrate to newer versions - esp as we drop support for older. Frictions such as this can be a reason to go elsewhere. I'm "pro" b/w compact - esp given our published guidelines. Patrick > Andor > > > > > > On 2020. Feb 10., at 11:32, Enrico Olivelli wrote: > > > > Thank you Mate for checking and explaining this story. > > > > I find it very interesting that the cause is ZOOKEEPER-3188 as: > > - it is the last "big patch" committed to 3.6 before starting the > > release process > > - it is the cause of the failure of the first RC > > > > In my experience when you are close to a release it is better to to > > make big changes. (I am among the approvers of that patch, so I am > > responsible for this change) > > > > This is a pointer to the change to whom who wants to understand better > > the context > > > https://github.com/apache/zookeeper/pull/1048/files#diff-7a209d890686bcba351d758b64b22a7dR11 > > > > IIUC even for the upgrade from 3.4 to 3.5 the story was the same and > > if this statement holds then I feel we can continue > > with this release. > > > > - Reverting ZOOKEEPER-3188 is not an option for me, it is too complex. > > - Making 3.5 and 3.6 "compatible" can be very tricky and we do not > > have tools to certify this compatibility (at least not in the short > > term) > > > > I would like to ear from people that have been in the community for > > long time, then I am ready to complete the release process for > > 3.6.0rc2. > > > > I will update the website and the release notes with a specific > > warning about the upgrade, we should also update the Wiki > > > > Enrico > > > > > > Il giorno lun 10 feb 2020 alle ore 11:17 Szalay-Bekő Máté > > ha scritto: > >> > >> Hi Enrico! > >> > >> This is caused by the different PROTOCOL_VERSION in the > QuorumCnxManager. > >> The Protocol version was changed last time in ZOOKEEPER-2186 released > >> first in 3.4.7 and 3.5.1 to avoid some crashing / fix some bugs. Later I > >> also changed the protocol version when the format of the initial message > >> changed in ZOOKEEPER-3188. So actually the quorum protocol is not > >> compatible in this case and is the 'expected' behavior if you upgrade > e.g > >> from 3.4.6 to 3.4.7, or 3.4.6 to 3.5.5 or e.g from 3.5.6 to 3.6.0. > >> > >> We had some discussion in the PR of ZOOKEEPER-3188 back then and got to > the > >> conclusion that it is not that bad, as there will be no data loss as you > >> wrote. The tricky thing is that during rolling upgrade we should ensure > >> both backward and forward compatibility to make sure that the old and > the > >> new part of the quorum can still speak to each other. The current > solution > >> (simply failing if the protocol versions mismatch) is more simple and > still > >> working just fine: as the servers are restarted one-by-one, the nodes > with > >> the old protocol version and the nodes with the new protocol version > will > >> form two partitions, but any given time only one partition will have the > >> quorum. > >> > >> Still, thinking it trough, as a side effect in these cases there will > be a > >> short time when none of the partitions will have quorums (when we have N > >> servers with the old protocol version, N servers with the new protocol > >> version, and there is one server just being restarted). I am not sure > if we > >> can accept this. > >> > >> For ZOOKEEPER-3188 we can add a small
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Hi, Answers inline. > In my experience when you are close to a release it is better to to > make big changes. (I am among the approvers of that patch, so I am > responsible for this change) Although this statement is acceptable for me, I don’t feel this patch should not have been merged into 3.6.0. Submission has been preceded by a long argument with MAPR folks who originally wanted to be merged into 3.4 branch (considering the pace how ZooKeeper community is moving forward) and we reached an agreement that release it with 3.6.0. Make a long story short, this patch has been outstanding for ages without much attention from the community and contributors made a lot of effort to get it done before the release. > I would like to ear from people that have been in the community for > long time, then I am ready to complete the release process for > 3.6.0rc2. Me too. I tend to accept the way rolling restart works now - as you described Enrico - and given that situation was pretty much the same between 3.4 and 3.5, I don’t feel we have to make additional changes. On the other hand, the fix that Mate suggested sounds quite cool, I’m also happy to work on getting it in. Fyi, Release Management page says the following: https://cwiki.apache.org/confluence/display/ZOOKEEPER/ReleaseManagement "major.minor release of ZooKeeper must be backwards compatible with the previous minor release, major.(minor-1)" Andor > On 2020. Feb 10., at 11:32, Enrico Olivelli wrote: > > Thank you Mate for checking and explaining this story. > > I find it very interesting that the cause is ZOOKEEPER-3188 as: > - it is the last "big patch" committed to 3.6 before starting the > release process > - it is the cause of the failure of the first RC > > In my experience when you are close to a release it is better to to > make big changes. (I am among the approvers of that patch, so I am > responsible for this change) > > This is a pointer to the change to whom who wants to understand better > the context > https://github.com/apache/zookeeper/pull/1048/files#diff-7a209d890686bcba351d758b64b22a7dR11 > > IIUC even for the upgrade from 3.4 to 3.5 the story was the same and > if this statement holds then I feel we can continue > with this release. > > - Reverting ZOOKEEPER-3188 is not an option for me, it is too complex. > - Making 3.5 and 3.6 "compatible" can be very tricky and we do not > have tools to certify this compatibility (at least not in the short > term) > > I would like to ear from people that have been in the community for > long time, then I am ready to complete the release process for > 3.6.0rc2. > > I will update the website and the release notes with a specific > warning about the upgrade, we should also update the Wiki > > Enrico > > > Il giorno lun 10 feb 2020 alle ore 11:17 Szalay-Bekő Máté > ha scritto: >> >> Hi Enrico! >> >> This is caused by the different PROTOCOL_VERSION in the QuorumCnxManager. >> The Protocol version was changed last time in ZOOKEEPER-2186 released >> first in 3.4.7 and 3.5.1 to avoid some crashing / fix some bugs. Later I >> also changed the protocol version when the format of the initial message >> changed in ZOOKEEPER-3188. So actually the quorum protocol is not >> compatible in this case and is the 'expected' behavior if you upgrade e.g >> from 3.4.6 to 3.4.7, or 3.4.6 to 3.5.5 or e.g from 3.5.6 to 3.6.0. >> >> We had some discussion in the PR of ZOOKEEPER-3188 back then and got to the >> conclusion that it is not that bad, as there will be no data loss as you >> wrote. The tricky thing is that during rolling upgrade we should ensure >> both backward and forward compatibility to make sure that the old and the >> new part of the quorum can still speak to each other. The current solution >> (simply failing if the protocol versions mismatch) is more simple and still >> working just fine: as the servers are restarted one-by-one, the nodes with >> the old protocol version and the nodes with the new protocol version will >> form two partitions, but any given time only one partition will have the >> quorum. >> >> Still, thinking it trough, as a side effect in these cases there will be a >> short time when none of the partitions will have quorums (when we have N >> servers with the old protocol version, N servers with the new protocol >> version, and there is one server just being restarted). I am not sure if we >> can accept this. >> >> For ZOOKEEPER-3188 we can add a small patch to make it possible to parse >> the initial message of the old protocol version with the new code. But I am >> not sure if it would be enough (as the old code will not be able to parse >> the new initial message). >> >> One option can be to make a patch also for 3.5 to have a version which >> supports both protocol versions. (let's say in 3.5.8) Then we can write to >> the release note, that if you need rolling upgrade from any versions since >> 3.4.7, then you have to first upgrade from
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Thank you Mate for checking and explaining this story. I find it very interesting that the cause is ZOOKEEPER-3188 as: - it is the last "big patch" committed to 3.6 before starting the release process - it is the cause of the failure of the first RC In my experience when you are close to a release it is better to to make big changes. (I am among the approvers of that patch, so I am responsible for this change) This is a pointer to the change to whom who wants to understand better the context https://github.com/apache/zookeeper/pull/1048/files#diff-7a209d890686bcba351d758b64b22a7dR11 IIUC even for the upgrade from 3.4 to 3.5 the story was the same and if this statement holds then I feel we can continue with this release. - Reverting ZOOKEEPER-3188 is not an option for me, it is too complex. - Making 3.5 and 3.6 "compatible" can be very tricky and we do not have tools to certify this compatibility (at least not in the short term) I would like to ear from people that have been in the community for long time, then I am ready to complete the release process for 3.6.0rc2. I will update the website and the release notes with a specific warning about the upgrade, we should also update the Wiki Enrico Il giorno lun 10 feb 2020 alle ore 11:17 Szalay-Bekő Máté ha scritto: > > Hi Enrico! > > This is caused by the different PROTOCOL_VERSION in the QuorumCnxManager. > The Protocol version was changed last time in ZOOKEEPER-2186 released > first in 3.4.7 and 3.5.1 to avoid some crashing / fix some bugs. Later I > also changed the protocol version when the format of the initial message > changed in ZOOKEEPER-3188. So actually the quorum protocol is not > compatible in this case and is the 'expected' behavior if you upgrade e.g > from 3.4.6 to 3.4.7, or 3.4.6 to 3.5.5 or e.g from 3.5.6 to 3.6.0. > > We had some discussion in the PR of ZOOKEEPER-3188 back then and got to the > conclusion that it is not that bad, as there will be no data loss as you > wrote. The tricky thing is that during rolling upgrade we should ensure > both backward and forward compatibility to make sure that the old and the > new part of the quorum can still speak to each other. The current solution > (simply failing if the protocol versions mismatch) is more simple and still > working just fine: as the servers are restarted one-by-one, the nodes with > the old protocol version and the nodes with the new protocol version will > form two partitions, but any given time only one partition will have the > quorum. > > Still, thinking it trough, as a side effect in these cases there will be a > short time when none of the partitions will have quorums (when we have N > servers with the old protocol version, N servers with the new protocol > version, and there is one server just being restarted). I am not sure if we > can accept this. > > For ZOOKEEPER-3188 we can add a small patch to make it possible to parse > the initial message of the old protocol version with the new code. But I am > not sure if it would be enough (as the old code will not be able to parse > the new initial message). > > One option can be to make a patch also for 3.5 to have a version which > supports both protocol versions. (let's say in 3.5.8) Then we can write to > the release note, that if you need rolling upgrade from any versions since > 3.4.7, then you have to first upgrade from 3.5.8 before upgrading to 3.6.0. > We can even make the same thing on the 3.4 branch. > > But I am also new to the community... It would be great to hear the opinion > of more experienced people. > Whatever the decision will be, I am happy to make the changes. > > And sorry for breaking the RC (if we decide that this needs to be > changed...). ZOOKEEPER-3188 was a complex patch. > > Kind regards, > Mate > > On Mon, Feb 10, 2020 at 9:47 AM Enrico Olivelli wrote: > > > Hi, > > even if we had enough binding +1 on 3.6.0rc2 before closing the VOTE > > of 3.6.0 I wanted to finish my tests and I am coming to an apparent > > blocker. > > > > I am trying to upgrade a 3.5.6 cluster to 3.6.0, but it looks like > > peers are not able to talk to each other. > > I have a cluster of 3, server1, server2 and server3. > > When I upgrade server1 to 3.6.0rc2 I see this kind of errors on 3.5 nodes: > > > > 2020-02-10 09:35:07,745 [myid:3] - INFO > > [localhost/127.0.0.1:3334:QuorumCnxManager$Listener@918] - Received > > connection request 127.0.0.1:62591 > > 2020-02-10 09:35:07,746 [myid:3] - ERROR > > [localhost/127.0.0.1:3334:QuorumCnxManager@527] - > > > > org.apache.zookeeper.server.quorum.QuorumCnxManager$InitialMessage$InitialMessageException: > > Got unrecognized protocol version -65535 > > > > Once I upgrade all of the peers the system is up and running, without > > apparently no data loss. > > > > During the upgrade as soon as I upgrade the first node, say, server1, > > server1 is not able to accept connections (error "Close of session 0x0 > > java.io.IOException: ZooKeeperServer not running") from
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Actually, we have an other option: we can follow the way, how the rolling restart support for the QuorumSSL was implemented. - we can make 3.6.0 to be able to read both protocol versions - we can add a parameter that tells the 3.6.0 which protocol version to use (using the old one brakes / disables the MultiAddress feature, but I think that is OK during upgrade) - then we can make a rolling upgrade with the old protocol version - then we can change the parameter to use the new protocol version (at this point all nodes can understand both versions) - then we can do a rolling restart with the new config I would vote on this solution. Kind regards, Mate On Mon, Feb 10, 2020 at 11:17 AM Szalay-Bekő Máté < szalay.beko.m...@gmail.com> wrote: > Hi Enrico! > > This is caused by the different PROTOCOL_VERSION in the QuorumCnxManager. > The Protocol version was changed last time in ZOOKEEPER-2186 released > first in 3.4.7 and 3.5.1 to avoid some crashing / fix some bugs. Later I > also changed the protocol version when the format of the initial message > changed in ZOOKEEPER-3188. So actually the quorum protocol is not > compatible in this case and is the 'expected' behavior if you upgrade e.g > from 3.4.6 to 3.4.7, or 3.4.6 to 3.5.5 or e.g from 3.5.6 to 3.6.0. > > We had some discussion in the PR of ZOOKEEPER-3188 back then and got to > the conclusion that it is not that bad, as there will be no data loss as > you wrote. The tricky thing is that during rolling upgrade we should ensure > both backward and forward compatibility to make sure that the old and the > new part of the quorum can still speak to each other. The current solution > (simply failing if the protocol versions mismatch) is more simple and still > working just fine: as the servers are restarted one-by-one, the nodes with > the old protocol version and the nodes with the new protocol version will > form two partitions, but any given time only one partition will have the > quorum. > > Still, thinking it trough, as a side effect in these cases there will be a > short time when none of the partitions will have quorums (when we have N > servers with the old protocol version, N servers with the new protocol > version, and there is one server just being restarted). I am not sure if we > can accept this. > > For ZOOKEEPER-3188 we can add a small patch to make it possible to parse > the initial message of the old protocol version with the new code. But I am > not sure if it would be enough (as the old code will not be able to parse > the new initial message). > > One option can be to make a patch also for 3.5 to have a version which > supports both protocol versions. (let's say in 3.5.8) Then we can write to > the release note, that if you need rolling upgrade from any versions since > 3.4.7, then you have to first upgrade from 3.5.8 before upgrading to 3.6.0. > We can even make the same thing on the 3.4 branch. > > But I am also new to the community... It would be great to hear the > opinion of more experienced people. > Whatever the decision will be, I am happy to make the changes. > > And sorry for breaking the RC (if we decide that this needs to be > changed...). ZOOKEEPER-3188 was a complex patch. > > Kind regards, > Mate > > On Mon, Feb 10, 2020 at 9:47 AM Enrico Olivelli > wrote: > >> Hi, >> even if we had enough binding +1 on 3.6.0rc2 before closing the VOTE >> of 3.6.0 I wanted to finish my tests and I am coming to an apparent >> blocker. >> >> I am trying to upgrade a 3.5.6 cluster to 3.6.0, but it looks like >> peers are not able to talk to each other. >> I have a cluster of 3, server1, server2 and server3. >> When I upgrade server1 to 3.6.0rc2 I see this kind of errors on 3.5 nodes: >> >> 2020-02-10 09:35:07,745 [myid:3] - INFO >> [localhost/127.0.0.1:3334:QuorumCnxManager$Listener@918] - Received >> connection request 127.0.0.1:62591 >> 2020-02-10 09:35:07,746 [myid:3] - ERROR >> [localhost/127.0.0.1:3334:QuorumCnxManager@527] - >> >> org.apache.zookeeper.server.quorum.QuorumCnxManager$InitialMessage$InitialMessageException: >> Got unrecognized protocol version -65535 >> >> Once I upgrade all of the peers the system is up and running, without >> apparently no data loss. >> >> During the upgrade as soon as I upgrade the first node, say, server1, >> server1 is not able to accept connections (error "Close of session 0x0 >> java.io.IOException: ZooKeeperServer not running") from clients, this >> is expected, because as far as it cannot talk with the other peers it >> is practically partitioned away from the cluster. >> >> My questions are: >> 1) is this expected ? I can't remember protocol changes from 3.5 to >> 3.6, but actually 3.6 diverged from 3.5 branch so long ago, and I was >> not in the community as dev so I cannot tell >> 2) is this a viable option for users ? to have some temporary glitch >> during the upgrade and hope that the upgrade completes without >> troubles ? >> >> In theory as long as two servers are running the same
Re: Rolling upgrade from 3.5 to 3.6 - expected behaviour
Hi Enrico! This is caused by the different PROTOCOL_VERSION in the QuorumCnxManager. The Protocol version was changed last time in ZOOKEEPER-2186 released first in 3.4.7 and 3.5.1 to avoid some crashing / fix some bugs. Later I also changed the protocol version when the format of the initial message changed in ZOOKEEPER-3188. So actually the quorum protocol is not compatible in this case and is the 'expected' behavior if you upgrade e.g from 3.4.6 to 3.4.7, or 3.4.6 to 3.5.5 or e.g from 3.5.6 to 3.6.0. We had some discussion in the PR of ZOOKEEPER-3188 back then and got to the conclusion that it is not that bad, as there will be no data loss as you wrote. The tricky thing is that during rolling upgrade we should ensure both backward and forward compatibility to make sure that the old and the new part of the quorum can still speak to each other. The current solution (simply failing if the protocol versions mismatch) is more simple and still working just fine: as the servers are restarted one-by-one, the nodes with the old protocol version and the nodes with the new protocol version will form two partitions, but any given time only one partition will have the quorum. Still, thinking it trough, as a side effect in these cases there will be a short time when none of the partitions will have quorums (when we have N servers with the old protocol version, N servers with the new protocol version, and there is one server just being restarted). I am not sure if we can accept this. For ZOOKEEPER-3188 we can add a small patch to make it possible to parse the initial message of the old protocol version with the new code. But I am not sure if it would be enough (as the old code will not be able to parse the new initial message). One option can be to make a patch also for 3.5 to have a version which supports both protocol versions. (let's say in 3.5.8) Then we can write to the release note, that if you need rolling upgrade from any versions since 3.4.7, then you have to first upgrade from 3.5.8 before upgrading to 3.6.0. We can even make the same thing on the 3.4 branch. But I am also new to the community... It would be great to hear the opinion of more experienced people. Whatever the decision will be, I am happy to make the changes. And sorry for breaking the RC (if we decide that this needs to be changed...). ZOOKEEPER-3188 was a complex patch. Kind regards, Mate On Mon, Feb 10, 2020 at 9:47 AM Enrico Olivelli wrote: > Hi, > even if we had enough binding +1 on 3.6.0rc2 before closing the VOTE > of 3.6.0 I wanted to finish my tests and I am coming to an apparent > blocker. > > I am trying to upgrade a 3.5.6 cluster to 3.6.0, but it looks like > peers are not able to talk to each other. > I have a cluster of 3, server1, server2 and server3. > When I upgrade server1 to 3.6.0rc2 I see this kind of errors on 3.5 nodes: > > 2020-02-10 09:35:07,745 [myid:3] - INFO > [localhost/127.0.0.1:3334:QuorumCnxManager$Listener@918] - Received > connection request 127.0.0.1:62591 > 2020-02-10 09:35:07,746 [myid:3] - ERROR > [localhost/127.0.0.1:3334:QuorumCnxManager@527] - > > org.apache.zookeeper.server.quorum.QuorumCnxManager$InitialMessage$InitialMessageException: > Got unrecognized protocol version -65535 > > Once I upgrade all of the peers the system is up and running, without > apparently no data loss. > > During the upgrade as soon as I upgrade the first node, say, server1, > server1 is not able to accept connections (error "Close of session 0x0 > java.io.IOException: ZooKeeperServer not running") from clients, this > is expected, because as far as it cannot talk with the other peers it > is practically partitioned away from the cluster. > > My questions are: > 1) is this expected ? I can't remember protocol changes from 3.5 to > 3.6, but actually 3.6 diverged from 3.5 branch so long ago, and I was > not in the community as dev so I cannot tell > 2) is this a viable option for users ? to have some temporary glitch > during the upgrade and hope that the upgrade completes without > troubles ? > > In theory as long as two servers are running the same major version > (3.5 or 3.6) we have a quorum and the system is able to make progress > and to server clients. > I feel that this is quite dangerous, but I don't have enough context > to understand how this problem is possible and when we decided to > break compatibility. > > The other option is that I am wrong in my test and I am messing up :-) > > The other upgrade path I would like to see working like a charm is the > upgrade from 3.4 to 3.6, as I see that as soon as we release 3.6 we > should encourage users to move to 3.6 and not to 3.5. > > Regards > Enrico >
